A065956 - OEIS

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A065956

a(n) = ceiling((-1)^n*n!*(E(n,2)-E(n,1)*E(n-1,1))) where E(n,x) = Sum_{k=0..n} (-1)^k*x^k/k!.

1, 1, 2, 3, 5, 9, 15, 27, 48, 87, 160, 296, 552, 1033, 1941, 3663, 6936, 13171, 25076, 47854, 91515, 175352, 336587, 647132, 1246070, 2402691, 4638909, 8967212, 17353538, 33618333, 65191863, 126535914, 245818071, 477938270, 929968029, 1810857391, 3528610690, 6880357956

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

OFFSET

0,3

LINKS

Table of n, a(n) for n=0..37.

EXAMPLE

1, 1, 2, 3, 5, 17/2, 89/6, 211/8, 1903/40, 62473/720, ...

MATHEMATICA

e[n_, x_]:=Sum[(-x)^k/k!, {k, 0, n}]; a[n_]:=Ceiling[(-1)^n*n!*(e[n, 2]-e[n, 1]e[n-1, 1])]; Array[a, 38, 0] (* Stefano Spezia, Apr 12 2024 *)

CROSSREFS

Cf. A065952, A065953, A065954, A065955.

Sequence in context: A022858 A301470 A090905 * A328078 A178738 A060013