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

Author

Antti Karttunen, May 08 2022

Keywords

• nonn
• look

Links

• Antti Karttunen, Table of n, a(n) for n = 1..20000
• Index entries for sequences related to sigma(n)

Crossrefs

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

Cf. also A353754.

Programs

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]))); };

Formula

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