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 A049389 a(n) = (n+8)!/8!. 18
 1, 9, 90, 990, 11880, 154440, 2162160, 32432400, 518918400, 8821612800, 158789030400, 3016991577600, 60339831552000, 1267136462592000, 27877002177024000, 641171050071552000, 15388105201717248000 (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=9) ~ exp(-x)/x*(1 - 9/x + 90/x^2 - 990/x^3 + 11880/x^4 - 154440/x^5 + ...) leads to the sequence given above. See A163931 and A130534 for more information. - Johannes W. Meijer, Oct 20 2009 a(n) = A173333(n+8,8). - Reinhard Zumkeller, Feb 19 2010 a(n) = A245334(n+8,n) / 9. - Reinhard Zumkeller, Aug 31 2014 LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..300 FORMULA a(n) = (n+8)!/8!. E.g.f.: 1/(1-x)^9. PROG (MAGMA) [Factorial(n+8)/40320: n in [0..25]]; // Vincenzo Librandi, Jul 20 2011 (PARI) a(n) = (n+8)!/8!; (Haskell) a049389 = (flip div 40320) . a000142 . (+ 8) -- Reinhard Zumkeller, Aug 31 2014 CROSSREFS Cf. A000142, A001710, A001715, A001720, A001725, A001730, A049388, A051379. a(n)= A051380(n, 0)*(-1)^n (first unsigned column of triangle). Cf. A245334. Sequence in context: A165324 A082367 A276506 * A127769 A276961 A062815 Adjacent sequences:  A049386 A049387 A049388 * A049390 A049391 A049392 KEYWORD easy,nonn AUTHOR STATUS approved

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Last modified February 17 17:59 EST 2020. Contains 331999 sequences. (Running on oeis4.)