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 A131491 #10 Aug 31 2025 18:22:57 %S A131491 4,12,240,10080,79833600,12454041600,711374856192000, %T A131491 243290200817664000,51704033477769953280000, %U A131491 17683523987479403909087232000000,16445677308355845635451125760000000,27527506182452690092631959163161804800000000 %N A131491 a(n) = 2*prime(n)!. %F A131491 a(n) = 2*A039716(n) = 2*A000142(A000040(n)). - _R. J. Mathar_, Jul 31 2007 %t A131491 2*Prime[Range[15]]! (* _Harvey P. Dale_, Dec 19 2011 *) %Y A131491 Cf. A000040, A000142, A039716. %K A131491 easy,nonn,changed %O A131491 1,1 %A A131491 _Giovanni Teofilatto_, Jul 29 2007 %E A131491 More terms from _Harvey P. Dale_, Dec 19 2011