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A356038 a(n) = Sum_{k=1..n} binomial(n,k) * sigma_2(k). 4
1, 7, 28, 95, 286, 802, 2143, 5519, 13807, 33762, 81060, 191678, 447396, 1032647, 2360593, 5351231, 12041764, 26920297, 59829006, 132262550, 290990077, 637429514, 1390811841, 3023647046, 6551547161, 14151910442, 30481920523, 65480947739, 140318385088, 299995596747 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..30.

Eric Weisstein's World of Mathematics, Divisor Function.

FORMULA

a(n) ~ zeta(3) * n^2 * 2^(n-2).

MATHEMATICA

Table[Sum[Binomial[n, k] * DivisorSigma[2, k], {k, 1, n}], {n, 1, 40}]

PROG

(PARI) a(n) = sum(k=1, n, binomial(n, k) * sigma(k, 2)); \\ Michel Marcus, Jul 24 2022

CROSSREFS

Cf. A001157, A160399, A185003, A356039.

Cf. A006218, A024916, A064602, A064603.

Sequence in context: A276236 A022572 A193654 * A241400 A219411 A224404

Adjacent sequences:  A356034 A356035 A356036 * A356039 A356040 A356041

KEYWORD

nonn

AUTHOR

Vaclav Kotesovec, Jul 24 2022

STATUS

approved

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Last modified October 3 07:14 EDT 2022. Contains 357231 sequences. (Running on oeis4.)