This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A238685 #14 Jun 09 2025 11:26:44 %S A238685 1,-6,210,-17640,2693880,-649479600,226750764240,-108116216208000, %T A238685 67478689070432640,-53382381970299782400,52192613508738839136000, %U A238685 -61794396463636399635072000,87121906773549083421777792000,-144222462676882552982237906688000 %N A238685 a(n) = n! * A129505(n) * (-1)^(n+1). %H A238685 Reinhard Zumkeller, <a href="/A238685/b238685.txt">Table of n, a(n) for n = 1..200</a> %F A238685 a(n) = A000142(n) * A008275(2*n-1,n). %F A238685 a(n) = A048594(2*n-1,n). %t A238685 Array[#!*StirlingS1[2 # - 1, #] &, 14] (* _Michael De Vlieger_, Jan 24 2022 *) %o A238685 (Haskell) %o A238685 a238685 n = a000142 n * a008275 (2 * n - 1) n %o A238685 (PARI) a(n) = n!*stirling(2*n-1,n, 1); \\ _Michel Marcus_, Jan 24 2022 %o A238685 (Python) %o A238685 from math import factorial %o A238685 from sympy.functions.combinatorial.numbers import stirling %o A238685 def A238685(n): return factorial(n)*stirling((n<<1)-1,n,kind=1,signed=True) # _Chai Wah Wu_, Jun 09 2025 %Y A238685 Cf. A000142, A008275, A048594, A129505. %K A238685 sign %O A238685 1,2 %A A238685 _Reinhard Zumkeller_, Mar 02 2014