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A049388 a(n) = (n+7)!/7!. 25
1, 8, 72, 720, 7920, 95040, 1235520, 17297280, 259459200, 4151347200, 70572902400, 1270312243200, 24135932620800, 482718652416000, 10137091700736000, 223016017416192000, 5129368400572416000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

The asymptotic expansion of the higher order exponential integral E(x,m=1,n=8) ~ exp(-x)/x*(1 - 8/x + 72/x^2 - 720/x^3 + 7920/x^4 - 95040/x^5 + 235520/x^6 - 17297280/x^7 + ...) leads to the sequence given above. See A163931 and A130534 for more information. - Johannes W. Meijer, Oct 20 2009

a(n) = A173333(n+7,7). - Reinhard Zumkeller, Feb 19 2010

a(n) = A245334(n+7,n) / 8. - Reinhard Zumkeller, Aug 31 2014

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..300

FORMULA

a(n) = (n+7)!/7!.

E.g.f.: 1/(1-x)^8.

MATHEMATICA

((Range[0, 20]+7)!)/7! (* Harvey P. Dale, Jul 31 2012 *)

PROG

(MAGMA) [Factorial(n+7)/5040: n in [0..25]]; // Vincenzo Librandi, Jul 20 2011

(Haskell)

a049388 = (flip div 5040) . a000142 . (+ 7)

-- Reinhard Zumkeller, Aug 31 2014

(PARI) vector(20, n, n--; (n+7)!/7!) \\ G. C. Greubel, Aug 15 2018

CROSSREFS

Cf. A000142, A001710, A001715, A001720, A001725, A001730, A051339. a(n)= A051379(n, 0)*(-1)^n (first unsigned column of triangle).

Cf. A245334.

Sequence in context: A165323 A082366 A221159 * A014479 A013992 A279156

Adjacent sequences:  A049385 A049386 A049387 * A049389 A049390 A049391

KEYWORD

easy,nonn

AUTHOR

Wolfdieter Lang

STATUS

approved

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Last modified February 15 23:33 EST 2019. Contains 320139 sequences. (Running on oeis4.)