A364560 - OEIS

%I #13 Jul 29 2023 15:59:18

%S 1,2,3,4,5,6,8,9,10,12,15,16,18,20,21,24,25,27,30,32,35,36,40,42,45,

%T 48,49,50,54,55,60,63,64,70,72,75,77,80,81,84,90,91,96,98,99,100,105,

%U 108,110,120,121,125,126,128,135,140,143,144,147,150,154,160,162,165,168,169,175,180,182,187,189,192,195,196

%N Numbers k for which A156552(k) < k.

%C Numbers k such that A005941(k) <= k.

%C Sequence A005940(A364542(.)) sorted into ascending order.

%C If k is a term, then also 2*k is present in this sequence, and vice versa.

%o (PARI)

%o A156552(n) = { my(f = factor(n), p, p2 = 1, res = 0); for(i = 1, #f~, p = 1 << (primepi(f[i, 1]) - 1); res += (p * p2 * (2^(f[i, 2]) - 1)); p2 <<= f[i, 2]); res };

%o isA364560(n) = (A156552(n) < n);

%Y Positions of nonpositive terms in A364559.

%Y Cf. A005941, A156552, A364542, A364562 (complement).

%Y Subsequences: A029747, A364550, A364561 (odd terms).

%K nonn

%O 1,2

%A _Antti Karttunen_, Jul 28 2023