A344974 - OEIS

%I #13 Jun 12 2021 06:06:16

%S 1,2,3,4,5,6,7,8,9,10,11,13,16,17,18,19,21,23,24,25,26,27,28,29,31,32,

%T 34,36,37,39,40,41,43,47,49,50,53,55,57,58,59,61,64,67,68,71,73,74,75,

%U 78,79,81,82,83,89,93,96,97,98,100,101,103,106,107,109,111,113,120,121,122,125,127,128,129,131,136,137

%N Numbers k such that A011772(k) divides A344875(k).

%t A011772[n_] := Module[{m = 1}, While[Not[IntegerQ[m(m+1)/(2n)]], m++]; m];

%t A344875[n_] := Product[{p, e} = pe; If[p == 2, 2^(1+e)-1, p^e-1], {pe, FactorInteger[n]}];

%t Select[Range[200], Divisible[A344875[#], A011772[#]]&] (* _Jean-François Alcover_, Jun 12 2021 *)

%o (PARI) isA344974(n) = (0==A344973(n));

%Y Cf. A011772, A344875, A344884 (characteristic function).

%Y Positions of ones in A344970, of zeros in A344973.

%Y Union of A000961 and A344975. Complement of A344980.

%Y Cf. also A344595 (subsequence).

%K nonn

%O 1,2

%A _Antti Karttunen_, Jun 04 2021