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A273878 Numerator of (2*(n+1)!/(n+2)). 0
1, 4, 3, 48, 40, 1440, 1260, 8960, 72576, 7257600, 6652800, 958003200, 889574400, 11623772160, 163459296000, 41845579776000, 39520825344000, 12804747411456000, 12164510040883200, 231704953159680000, 4644631106519040000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

The moments, i.e. E(X^n) = int(x^n * p(x), x = 0..infinity) for n > 0, of the probability density function p(x) = 2*x*E(x, 1, 1), see A163931, lead to this sequence.

LINKS

Table of n, a(n) for n=0..20.

J. W. Meijer and N. H. G. Baken, The Exponential Integral Distribution, Statistics and Probability Letters, Volume 5, No.3, April 1987. pp 209-211.

FORMULA

a(n) = numer(2*(n+1)!/(n+2))

a(n) = (n+1) * A090586(n+1)

a(2*n) = A110468(n) and a(2*n+1) = (2*n)!*A085250(n+1)/A128060(n+2).

EXAMPLE

The first few moments of p(x) are: 1, 4/3, 3, 48/5, 40, 1440/7, … .

MAPLE

a := proc(n): numer(2*(n+1)!/(n+2)) end: seq(a(n), n=0..20);

PROG

(PARI) a(n) = numerator(2*(n+1)!/(n+2)) \\ Felix Fröhlich, Jun 09 2016

CROSSREFS

Cf. A090585 (denominators), A090586, A085250, A110468, A128059, A128060, A163931.

Sequence in context: A324671 A249226 A328193 * A013335 A298314 A299389

Adjacent sequences:  A273875 A273876 A273877 * A273879 A273880 A273881

KEYWORD

nonn,frac,easy

AUTHOR

Johannes W. Meijer, Jun 08 2016

STATUS

approved

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Last modified August 10 01:38 EDT 2020. Contains 336361 sequences. (Running on oeis4.)