A353804 Greatest common divisor of sigma(sigma(n)) and Product_{p^e||n} sigma(sigma(p^e)), where n = Product_{p^e||n}, with each p^e the maximal power of prime p that divides n.

1, 4, 7, 8, 12, 28, 15, 24, 14, 3, 28, 56, 24, 60, 12, 32, 39, 56, 42, 96, 21, 7, 60, 168, 32, 96, 90, 120, 72, 3, 63, 104, 4, 12, 4, 112, 60, 168, 24, 18, 96, 84, 84, 224, 168, 15, 124, 224, 80, 128, 39, 3, 120, 360, 3, 360, 6, 18, 168, 96, 96, 252, 210, 128, 32, 1, 126, 312, 84, 1, 195, 336, 114, 240, 224, 336

Offset

1,2

Links

Antti Karttunen, Table of n, a(n) for n = 1..20000

Index entries for sequences related to sigma(n)

Formula

a(n) = gcd(A051027(n), A353802(n)) = gcd(A051027(n), A353803(n)) = gcd(A353802(n), A353803(n)).

Prog

(PARI)
A051027(n) = sigma(sigma(n));
A353804(n) = { my(f = factor(n)); gcd(A051027(n), prod(k=1, #f~, A051027(f[k, 1]^f[k, 2]))); };

Crossrefs

Cf. A000203, A051027, A353802, A353803, A353805, A353806.

Cf. also A353754.

Sequence in context: A093494 A310934 A310935 * A051027 A353802 A291402

Adjacent sequences: A353801 A353802 A353803 * A353805 A353806 A353807

Keyword

nonn,look

Author

Antti Karttunen, May 08 2022

Status

approved