The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A070008 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A070008

Arithmetic mean of distinct primes dividing n is a power of 2 (powers of 2 are not left out).
(history; published version)

#13 by N. J. A. Sloane at Sat Mar 28 22:36:31 EDT 2015

STATUS

proposed

approved

#12 by Michael De Vlieger at Sat Mar 28 09:36:16 EDT 2015

STATUS

editing

proposed

#11 by Michael De Vlieger at Sat Mar 28 09:36:07 EDT 2015

LINKS

Michael De Vlieger, <a href="/A070008/b070008.txt">Table of n, a(n) for n = 1..3000</a>

STATUS

proposed

editing

#10 by Michael De Vlieger at Sat Mar 28 09:16:19 EDT 2015

STATUS

editing

proposed

#9 by Michael De Vlieger at Sat Mar 28 09:06:52 EDT 2015

MATHEMATICA

fQ[n_] := Block[{pf = FactorInteger@ n}, Length@ pf == 1 && pf[[1, 1]] == 2]; Select[Range[2, 780], fQ[Total[First /@ FactorInteger@#]/PrimeNu@#] &] (* Michael De Vlieger, Mar 28 2015 *)

STATUS

reviewed

editing

#8 by Wesley Ivan Hurt at Sat Mar 28 08:25:25 EDT 2015

STATUS

proposed

reviewed

#7 by Michel Marcus at Sat Mar 28 03:52:30 EDT 2015

STATUS

editing

proposed

#6 by Michel Marcus at Sat Mar 28 03:52:26 EDT 2015

NAME

Arithmetical Arithmetic mean of distinct primes dividing n is a power of 2 (n=powers of 2 are not left out).

EXAMPLE

n=9189=3.*1021, mean=(3+1021)/2=512.

CROSSREFS

Cf. A070005-, A070006, A070007, A008472, A001414.

STATUS

approved

editing

#5 by N. J. A. Sloane at Tue Oct 15 22:31:18 EDT 2013

AUTHOR

_Labos E. (labos(AT)ana.sote.hu), Elemer_, Apr 11 2002

Discussion

Tue Oct 15

22:31

OEIS Server: https://oeis.org/edit/global/2029

#4 by N. J. A. Sloane at Fri Feb 24 03:00:00 EST 2006

MATHEMATICA

ffi[x_] := Flatten[FactorInteger[x]] lf[x_] := Length[FactorInteger[x]] ba[x_] := Table[Part[ffi[x], 2*w-1], {w, 1, lf[x]}] Do[s=Apply[Plus, ba[n]]/lf[n]; If[IntegerQ[Log[2, s]], Print[{n, s}]], {n, 2, 10000}]

KEYWORD

nonn,new

nonn