A377990 a(n) = sigma(sigma(A350388(n))) * sigma(sigma(A350389(n))), where A350388 and A350389 are the largest unitary divisor of n that is a square, and the largest unitary divisor of n that is an exponentially odd number, respectively.

1, 4, 7, 8, 12, 28, 15, 24, 14, 39, 28, 56, 24, 60, 60, 32, 39, 56, 42, 96, 63, 91, 60, 168, 32, 96, 90, 120, 72, 195, 63, 104, 124, 120, 124, 112, 60, 168, 120, 234, 96, 252, 84, 224, 168, 195, 124, 224, 80, 128, 195, 192, 120, 360, 195, 360, 186, 234, 168, 480, 96, 252, 210, 128, 224, 403, 126, 312, 252, 403, 195

Offset

1,2

Comments

Differs from A051027 at 52, 98, 156, 164, 245, ..., = A377991.

Links

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

Index entries for sequences related to sigma(n)

Formula

a(n) = A051027(A350388(n)) * A051027(A350389(n)).

a(n) = sigma(A351568(n)) * sigma(A351569(n)).

Prog

(PARI)
A350388(n) = { my(m=1, f=factor(n)); for(k=1, #f~, if(0==(f[k, 2]%2), m *= (f[k, 1]^f[k, 2]))); (m); };
A350389(n) = { my(m=1, f=factor(n)); for(k=1, #f~, if(1==(f[k, 2]%2), m *= (f[k, 1]^f[k, 2]))); (m); };
A377990(n) = (sigma(sigma(A350388(n))) * sigma(sigma(A350389(n))));

Crossrefs

Cf. A000203, A051027, A350388, A350389, A351568, A351569, A377991.

Sequence in context: A310935 A353804 A051027 * A353802 A291402 A328792

Adjacent sequences: A377987 A377988 A377989 * A377991 A377992 A377993

Keyword

nonn

Author

Antti Karttunen, Nov 15 2024

Status

approved