A278784 - OEIS

%I #15 May 25 2024 09:09:42

%S 109,230,557,675,1094,1679,2070,2314,2594,2781,2873,3133,3498,3548,

%T 3595,3601,3629,3911,4059,4171,4264,4274,4501,4568,4878,4889,5112,

%U 5136,5507,5675,5907,6059,6152,6260,6490,6667,6669,6938,6961,7667,8013,8640,8729,9171

%N Numbers m such that A000041(m) is of the form 2^7 * k for odd k.

%C Numbers m such that A278478(m) = 7.

%C Also numbers m such that A000041(m) has seven times as many even divisors as odd divisors.

%H Colin Barker, <a href="/A278784/b278784.txt">Table of n, a(n) for n = 1..100</a>

%F A000041(a(n)) = A278201(n).

%t Select[Range[5000], IntegerExponent[PartitionsP[#], 2] == 7 &] (* _Amiram Eldar_, May 25 2024 *)

%o (PARI) isok(n) = valuation(numbpart(n), 2)==7;

%o select(n->isok(n), vector(9000, n, n))

%Y Cf. A000041, A278201, A278779, A278780, A278781, A278782, A278783.

%Y Positions of 7's in A278478.

%K nonn

%O 1,1

%A _Colin Barker_, Nov 28 2016