A168649 - OEIS

A168649

a(n) = (1/n)*Sum_{d|n} moebius(d)*2^(n^2/d).

2, 6, 168, 16320, 6710880, 11453201760, 80421421917312, 2305843008676823040, 268650182136584246132736, 126765060022822827559679531520, 241677817415439249618874010960062464, 1858395433210885261794249658823668075069440

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OFFSET

1,1

LINKS

Table of n, a(n) for n=1..12.

FORMULA

a(n) = (1/n)*Sum_{d|n} moebius(n/d)*(2^n)^d.

MATHEMATICA

a[n_] := DivisorSum[n, MoebiusMu[#] * 2^(n^2/#) &] / n; Array[a, 10] (* Amiram Eldar, Aug 18 2023 *)

PROG

(PARI) a(n)=(1/n)*sumdiv(n, d, moebius(d)*2^(n^2/d))

CROSSREFS

Cf. A001037, A008683.

Sequence in context: A281819 A329980 A199482 * A135937 A182523 A137532

Adjacent sequences: A168646 A168647 A168648 * A168650 A168651 A168652

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Dec 01 2009

EXTENSIONS

a(12) from Amiram Eldar, Aug 18 2023

STATUS

approved