A378996 Denominator of sigma(2*n)/(2*n).

2, 4, 1, 8, 5, 3, 7, 16, 6, 10, 11, 2, 13, 1, 5, 32, 17, 36, 19, 4, 7, 11, 23, 12, 50, 26, 9, 7, 29, 5, 31, 64, 11, 34, 35, 24, 37, 19, 13, 40, 41, 3, 43, 22, 5, 23, 47, 8, 98, 100, 17, 52, 53, 27, 55, 14, 19, 58, 59, 1, 61, 31, 21, 128, 65, 11, 67, 68, 23, 5, 71, 144, 73, 74, 25, 38, 77, 39, 79, 80, 54, 82, 83, 7

Offset: 1

Author

Antti Karttunen, Dec 13 2024

Keywords

• nonn
• frac
• easy

Links

• Antti Karttunen, Table of n, a(n) for n = 1..32769
• Index entries for sequences related to sigma(n).

Crossrefs

Even bisection of A017666.

Topmost row of array A341606.

Cf. A378994, A378995 (numerators).

Cf. also A336849.

Programs

Mathematica

a[n_] := Denominator[DivisorSigma[-1, 2*n]]; Array[a, 100] (* Amiram Eldar, Dec 14 2024 *)

PARI

A378996(n) = denominator(sigma(2*n)/(2*n));

Formula

a(n) = A017666(2*n).

a(n) = 2*n / A378994(n).