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A338684 a(n) = Sum_{d|n} (-1)^(d-1) * (n/d)^n * binomial(d+n/d-1, d). 4
1, 7, 82, 975, 15626, 275817, 5764802, 133561087, 3486981232, 99853521768, 3138428376722, 106947820494048, 3937376385699290, 155549105311903523, 6568409424129452048, 295137771929866797055, 14063084452067724991010, 708228596784096039676230, 37589973457545958193355602 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..19.

FORMULA

G.f.: Sum_{k >= 1} (1 - 1/(1 + (k * x)^k)^k).

If p is prime, a(p) = (-1)^(p-1) + p^(p+1).

MATHEMATICA

a[n_] := DivisorSum[n, (-1)^(# - 1) * (n/#)^n * Binomial[# + n/# - 1, #] &]; Array[a, 20] (* Amiram Eldar, Apr 24 2021 *)

PROG

(PARI) a(n) = sumdiv(n, d, (-1)^(d-1)*(n/d)^n*binomial(d+n/d-1, d));

(PARI) N=20; x='x+O('x^N); Vec(sum(k=1, N, 1-1/(1+(k*x)^k)^k))

CROSSREFS

Cf. A338663, A338682, A338683, A338685, A338689.

Sequence in context: A355220 A285062 A253265 * A304870 A191804 A243672

Adjacent sequences:  A338681 A338682 A338683 * A338685 A338686 A338687

KEYWORD

nonn

AUTHOR

Seiichi Manyama, Apr 23 2021

STATUS

approved

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Last modified August 8 14:59 EDT 2022. Contains 356009 sequences. (Running on oeis4.)