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A180221 Numbers that can be written as sum of one or more distinct elements of A000043. Numbers k for which sigma(A180162(k))=2^k, k>=2. 6

%I #15 Jun 02 2020 08:50:40

%S 2,3,5,7,8,9,10,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,

%T 30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,

%U 53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75

%N Numbers that can be written as sum of one or more distinct elements of A000043. Numbers k for which sigma(A180162(k))=2^k, k>=2.

%C The distinct values of log_2(sigma(m)), where m > 1 is a term of A046528. - _Amiram Eldar_, Jun 02 2020

%H Amiram Eldar, <a href="/A180221/b180221.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1855 from Walter A. Kehowski)

%t n = 10; p = MersennePrimeExponent[Range[n]]; Rest[-1 + Position[CoefficientList[Series[Product[(1 + x^p[[k]]), {k, 1, n}], {x, 0, p[[-1]]}], x], _?(# > 0 &)] // Flatten] (* _Amiram Eldar_, Jun 02 2020 *)

%Y Cf. A000043, A180162, A046528, A180169. Complement of A078426.

%K nonn

%O 1,1

%A _Walter Kehowski_, Aug 16 2010

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Last modified May 2 12:49 EDT 2024. Contains 372196 sequences. (Running on oeis4.)