

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 209211.


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



