A174940 - OEIS

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A174940

a(n) = Sum_{d|n} A007955(d) * A008683(n/d) = Sum_{d|n} A007955(d) * mu(n/d), where A007955(m) = number of divisors of m.

1, 1, 2, 6, 4, 32, 6, 56, 24, 94, 10, 1686, 12, 188, 218, 960, 16, 5772, 18, 7894, 432, 472, 22, 329992, 120, 662, 702, 21750, 28, 809648, 30, 31744, 1076, 1138, 1214, 10070172, 36, 1424, 1506, 2551944, 40, 3111034, 42, 84694, 90876, 2092, 46, 254471232, 336, 124780

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,3

LINKS

Andrew Howroyd, Table of n, a(n) for n = 1..1000

FORMULA

Moebius transform of A007955. - Andrew Howroyd, Jan 05 2020

EXAMPLE

For n = 4, A007955(n) = b(n): a(4) = b(1)*mu(4/1) + b(2)*mu(4/2) + b(4)*mu(4/4) = 1*0 + 2*(-1) + 8*1 = 6.

MATHEMATICA

a[n_] := Sum[ MoebiusMu[n/d] * Times @@ Divisors[d], {d, Divisors[n]} ]; Table[ a[n], {n, 1, 30} ] (* Jean-François Alcover, Jan 09 2013 *)

PROG

(PARI) a(n)={sumdiv(n, d, vecprod(divisors(d))*moebius(n/d))} \\ Andrew Howroyd, Jan 05 2020

(Magma) [&+[&*Divisors(d)*MoebiusMu(n div d):d in Divisors(n)]:n in [1..50]]; // Marius A. Burtea, Jan 05 2020

CROSSREFS

Cf. A008683 (mu), A007955 (product of divisors).

Sequence in context: A108951 A181822 A346107 * A293011 A108435 A322827

Adjacent sequences: A174937 A174938 A174939 * A174941 A174942 A174943

KEYWORD

nonn

AUTHOR

Jaroslav Krizek, Apr 02 2010

EXTENSIONS

Terms a(31) and beyond from Andrew Howroyd, Jan 05 2020

STATUS

approved