A332444 -id:A332444 - cp's OEIS frontend

A332443 Numbers k such that A332224(k) = A087808(sigma(k)) is odd.

1, 4, 9, 16, 18, 25, 49, 50, 64, 81, 100, 121, 169, 200, 256, 338, 361, 392, 400, 441, 450, 529, 578, 625, 648, 676, 722, 729, 784, 800, 841, 900, 961, 1024, 1089, 1156, 1225, 1250, 1296, 1352, 1369, 1568, 1600, 1682, 1800, 1849, 2025, 2116, 2209, 2312, 2401, 2450, 2592, 2601, 2704, 2738, 3042, 3136, 3200, 3249, 3362, 3364, 3481, 3600

Offset: 1

Antti Karttunen, Feb 13 2020

nonn

Numbers k such that A332224(k) is odd, or equally, that A332448(k) is zero.

Antti Karttunen, Table of n, a(n) for n = 1..26213
Index entries for sequences related to sigma(n)

Cf. A000203, A087808, A332224, A332225, A332444.

Subsequence of A028982. Positions of zeros in A332448.

A087808(n) = if(n<1, 0, if(n%2==0, 2*A087808(n/2), A087808((n-1)/2)+1));
isA332443(n) = (A087808(sigma(n))%2);
A332443list(u) = { my(v1=vector(2*u,n,2*(n^2)), v2=vector(sqrtint(v1[#v1]),n,n^2)); select(isA332443,Vec(setunion(v1,v2))); };
v332443 = A332443list(8192);
A332443(n) = v332443[n];

cp's OEIS Frontend

A332443 Numbers k such that A332224(k) = A087808(sigma(k)) is odd.

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