The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A061208 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
Showing entries 1-10 | older changes

A061208

Numbers which can be expressed as sum of distinct triangular numbers (A000217).
(history; published version)

#11 by N. J. A. Sloane at Thu Dec 05 19:54:49 EST 2013

AUTHOR

_Amarnath Murthy (amarnath_murthy(AT)yahoo.com), _, Apr 21 2001

Discussion

Thu Dec 05

19:54

OEIS Server: https://oeis.org/edit/global/2075

#10 by T. D. Noe at Tue Feb 05 19:16:08 EST 2013

STATUS

editing

approved

#9 by T. D. Noe at Tue Feb 05 19:15:54 EST 2013

COMMENTS

These numbers were called "almost-triangular" numbers during the Peru's Selection Test for the XII IberoAmerican Olympiad (1998). All numbers >= 34 are almost-triangular : see link . [Bernard Schott, Feb 04 2013]

LINKS

R. E. Woodrow, <a href="http://cms.math.ca/crux/v25/n4/page196-211.pdf">The Olympiad Corner, N°No. 198</a>, Crux Mathematicorum, v25-n4(2002), 207-208, exercise 2.

STATUS

proposed

editing

#8 by Bernard Schott at Mon Feb 04 08:38:22 EST 2013

STATUS

editing

proposed

#7 by Bernard Schott at Mon Feb 04 08:38:03 EST 2013

COMMENTS

These numbers were called "almost-triangular" numbers during the Peru's Selection Test for the XII IberoAmerican Olympiad [(1998:131]). All numbers >= 34 are almost-triangular : see link [Bernard Schott, Feb 04 2013]

FORMULA

25 = 1 + 3 + 6 + 15

EXAMPLE

27=

25 = 1 + 3 + 6 + 15

#6 by Bernard Schott at Mon Feb 04 07:56:24 EST 2013

COMMENTS

These numbers were called "almost-triangular" numbers during the Peru's Selection Test for the XII IberoAmerican Olympiad [1998:131]. All numbers >= 34 are almost-triangular : see link [Bernard Schott, Feb 04 2013]

FORMULA

25 = 1 + 3 + 6 + 15

EXAMPLE

27=

#5 by Bernard Schott at Mon Feb 04 07:48:30 EST 2013

COMMENTS

LINKS

R.E. Woodrow, <a href="http://cms.math.ca/crux/v25/n4/page196-211.pdf">The Olympiad Corner, N°198</a>, Crux Mathematicorum, v25-n4(2002), 207-208, exercise 2.

STATUS

approved

editing

#4 by Russ Cox at Sat Mar 31 10:30:32 EDT 2012

EXTENSIONS

Corrected and extended by _James A. Sellers (sellersj(AT)math.psu.edu), _, Apr 24 2001

Discussion

Sat Mar 31

10:30

OEIS Server: https://oeis.org/edit/global/639

#3 by N. J. A. Sloane at Fri Sep 29 03:00:00 EDT 2006

OFFSET

0,1,2

CROSSREFS

Cf. A000217, A007294, A051611, A051533, A053614. Complement of A066614A053614.

KEYWORD

nonn,new

nonn

#2 by N. J. A. Sloane at Sat Jun 12 03:00:00 EDT 2004

MAPLE

gf := product(1+x^(j*(j+1)/2), j=1..100): s := series(gf, x, 200): for i from 1 to 200 do if coeff(s, x, i) > 0 then printf(`%d, `, i) fi:od:

KEYWORD

nonn,new

nonn