# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/ Search: id:a049388 Showing 1-1 of 1 %I A049388 #30 Jan 15 2023 02:41:20 %S A049388 1,8,72,720,7920,95040,1235520,17297280,259459200,4151347200, %T A049388 70572902400,1270312243200,24135932620800,482718652416000, %U A049388 10137091700736000,223016017416192000,5129368400572416000,123104841613737984000,3077621040343449600000,80018147048929689600000 %N A049388 a(n) = (n+7)!/7!. %C A049388 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 %H A049388 Vincenzo Librandi, Table of n, a(n) for n = 0..300 %F A049388 a(n)= A051379(n, 0)*(-1)^n (first unsigned column of triangle). %F A049388 a(n) = (n+7)!/7!. %F A049388 E.g.f.: 1/(1-x)^8. %F A049388 a(n) = A173333(n+7,7). - _Reinhard Zumkeller_, Feb 19 2010 %F A049388 a(n) = A245334(n+7,n) / 8. - _Reinhard Zumkeller_, Aug 31 2014 %F A049388 From _Amiram Eldar_, Jan 15 2023: (Start) %F A049388 Sum_{n>=0} 1/a(n) = 5040*e - 13699. %F A049388 Sum_{n>=0} (-1)^n/a(n) = 1855 - 5040/e. (End) %t A049388 ((Range[0,20]+7)!)/7! (* _Harvey P. Dale_, Jul 31 2012 *) %o A049388 (Magma) [Factorial(n+7)/5040: n in [0..25]]; // _Vincenzo Librandi_, Jul 20 2011 %o A049388 (Haskell) %o A049388 a049388 = (flip div 5040) . a000142 . (+ 7) %o A049388 -- _Reinhard Zumkeller_, Aug 31 2014 %o A049388 (PARI) vector(20,n,n--; (n+7)!/7!) \\ _G. C. Greubel_, Aug 15 2018 %Y A049388 Cf. A000142, A001710, A001715, A001720, A001725, A001730, A051339, A051379. %Y A049388 Cf. A130534, A163931, A173333, A245334. %K A049388 easy,nonn %O A049388 0,2 %A A049388 _Wolfdieter Lang_ # Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE