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Revisions by G. C. Greubel (See also G. C. Greubel's wiki page)

(Bold, blue-underlined text is an addition; faded, red-underlined text is a deletion.)

Showing entries 1-10 | older changes
Sierpiński's [Sierpinski's] triangle (or gasket): triangle, read by rows, formed by reading Pascal's triangle (A007318) mod 2.
(history; published version)
#302 by G. C. Greubel at Tue Dec 03 13:54:49 EST 2024
STATUS

editing

proposed

#301 by G. C. Greubel at Tue Dec 03 13:54:34 EST 2024
PROG

(Magma)

A047999:= func< n, k | BitwiseAnd(n-k, k) eq 0 select 1 else 0 >;

[A047999(n, k): k in [0..n], n in [0..15]]; // G. C. Greubel, Dec 03 2024

STATUS

approved

editing

Triangle read by rows, Sierpinski's gasket, A047999 * (1,2,4,8,...) diagonalized.
(history; published version)
#14 by G. C. Greubel at Tue Dec 03 13:53:24 EST 2024
STATUS

editing

proposed

#13 by G. C. Greubel at Tue Dec 03 13:30:41 EST 2024
NAME

Triangle read by rows, Sierpinski's gasket, T(n, k) = 2^k * A047999 * (1,2,4,8,...n, k) diagonalized.

COMMENTS

Former name: Triangle read by rows, Sierpinski's gasket, A047999 * (1,2,4,8,...) diagonalized. - G. C. Greubel, Dec 02 2024

FORMULA

T(n, n) = A000079(n).

T(2*n, n) = A000007(n).

CROSSREFS

Cf. A000007, A000079, A000120, A001317, A038183, A101624, A101625, A147999.

Sums include: A001317 (row), A101624 (diagonal), A101625 (odd rows of signed diagonal).

EXTENSIONS

New name by G. C. Greubel, Dec 02 2024

STATUS

proposed

editing

Number of reduced words of length n in Coxeter group on 15 generators S_i with relations (S_i)^2 = (S_i S_j)^12 = I.
(history; published version)
#12 by G. C. Greubel at Tue Dec 03 03:58:46 EST 2024
STATUS

editing

proposed

#11 by G. C. Greubel at Tue Dec 03 03:58:42 EST 2024
MATHEMATICA

CoefficientList[Series[(1+x)*(1-x^12)/(1 - 14*x + 104*x^12 - 91*x^13), {t, 0, 50}], t](* G. C. Greubel, May 17 2016 ; Dec 03 2024 *)

#10 by G. C. Greubel at Tue Dec 03 03:58:17 EST 2024
LINKS

<a href="/index/Rec#order_12">Index entries for linear recurrences with constant coefficients</a>, signature (13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, -91).

FORMULA

From G. C. Greubel, Dec 03 2024: (Start)

a(n) = 13*Sum_{j=1..11} a(n-j) - 91*a(n-12).

G.f.: (1+x)*(1-x^12)/(1 - 14*x + 104*x^12 - 91*x^13). (End)

MATHEMATICA

CoefficientList[Series[(t1+x)*(1-x^12 + 2*t^11 + 2*t^10 + 2*t^9 + 2*t^8 + 2*t^7 + 2*t^6 + 2*t^5 + 2*t^4 + 2*t^3 + 2*t^2 + 2*t + )/(1)/(91 - 14*x + 104*tx^12 - 13*t^11 - 13*t^10 - 13*t^9 - 13*t^8 - 13*t^7 - 13*t^6 - 13*t^5 - 13*t^4 - 13*t^3 - 1391*tx^2 - 13*t + 1), {t, 0, 50}], t](* G. C. Greubel, May 17 2016 *)

coxG[{12, 91, -13}] (* The coxG program is at A169452 *) (* G. C. Greubel, Dec 03 2024 *)

PROG

(Magma)

R<x>:=PowerSeriesRing(Integers(), 40);

Coefficients(R!( (1+x)*(1-x^12)/(1-14*x+104*x^12-91*x^13) )); // G. C. Greubel, Dec 03 2024

(SageMath)

def A166583_list(prec):

P.<x> = PowerSeriesRing(ZZ, prec)

return P( (1+x)*(1-x^12)/(1-14*x+104*x^12-91*x^13) ).list()

A166583_list(40) # G. C. Greubel, Dec 03 2024

CROSSREFS
STATUS

approved

editing

Number of reduced words of length n in Coxeter group on 14 generators S_i with relations (S_i)^2 = (S_i S_j)^12 = I.
(history; published version)
#14 by G. C. Greubel at Tue Dec 03 03:47:54 EST 2024
STATUS

editing

proposed

#13 by G. C. Greubel at Tue Dec 03 03:47:32 EST 2024
LINKS

<a href="/index/Rec#order_12">Index entries for linear recurrences with constant coefficients</a>, signature (12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, -78).

FORMULA

From G. C. Greubel, Dec 03 2024: (Start)

a(n) = 12*Sum_{j=1..11} a(n-j) - 78*a(n-12).

G.f.: (1+x)*(1-x^12)/(1 - 13*x + 90*x^12 - 78*x^13). (End)

MATHEMATICA

CoefficientList[Series[(t^12 + 2*t^11 + 2*t^10 + 2*t^9 + 2*t^8 + 2*t^7 + 2*t^6 + 2*t^5 + 2*t^4 + 2*t^3 1+ 2*t^2 + 2)*t + (1)/(78*t^12 - 12*t^11 - 12*t^10 - 12*t^9 - 12*t^8 - 12*t^7 - 12*t^6 )/(1- 1213*t^5 - 12+90*t^4 - 12*t^3 - 1278*t^2 - 12*t + 113), {t, 0, 50}], t] (* G. C. Greubel, May 17 2016 ; Dec 03 2024 *)

PROG

(Magma)

R<x>:=PowerSeriesRing(Integers(), 40);

Coefficients(R!( (1+x)*(1-x^12)/(1-13*x+90*x^12-78*x^13) )); // G. C. Greubel, Dec 03 2024

(SageMath)

def A166568_list(prec):

P.<x> = PowerSeriesRing(ZZ, prec)

return P( (1+x)*(1-x^12)/(1-13*x+90*x^12-78*x^13) ).list()

A166568_list(40) # G. C. Greubel, Dec 03 2024

CROSSREFS
STATUS

approved

editing

Number of reduced words of length n in Coxeter group on 13 generators S_i with relations (S_i)^2 = (S_i S_j)^12 = I.
(history; published version)
#14 by G. C. Greubel at Tue Dec 03 03:13:22 EST 2024
STATUS

editing

proposed