A347875 Numbers k such that A323905(sigma(k)) is equal to A323905(2*k).

1, 6, 21, 28, 496, 8128

Offset

1,2

Comments

Numbers k such that A323905(sigma(k)) = A332221(k) - A331750(k) is equal to 2*A156552(k) - A048675(k) = A156552(k) + A323905(k).

Links

Table of n, a(n) for n=1..6.

Index entries for sequences where odd perfect numbers must occur, if they exist at all

Prog

(PARI)
A048675(n) = { my(f = factor(n)); sum(k=1, #f~, f[k, 2]*2^primepi(f[k, 1]))/2; }; \\ From A048675
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}; \\ From A156552
A323905(n) = (A156552(n) - A048675(n));
isA347875(n) = (A323905(sigma(n))==A323905(2*n));

Crossrefs

Cf. A000203, A048675, A156552, A323905, A347876.

Cf. also A000396 (subsequence), A331751, A347392.

Sequence in context: A143322 A246544 A034897 * A287165 A280296 A325407

Adjacent sequences: A347872 A347873 A347874 * A347876 A347877 A347878

Keyword

nonn,more

Author

Antti Karttunen, Sep 19 2021

Status

approved