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 A070734 #14 Aug 05 2025 21:33:06
%S A070734 3,24,60,720,2520,40320,181440,3628800,19958400,479001600,3113510400,
%T A070734 87178291200,653837184000,20922789888000,177843714048000,
%U A070734 6402373705728000,60822550204416000,2432902008176640000
%N A070734 Order of the subgroup of the symmetric group S_n generated by the cycles (1,2,3) and (1,2,3,...,n).
%F A070734 For odd n: a(n) = n!/2; for even n: a(n) = n!.
%F A070734 a(n) = (1/4)*(3+(-1)^n)*n! - _Benoit Cloitre_, May 18 2002
%F A070734 From _Amiram Eldar_, Jul 06 2022: (Start)
%F A070734 Sum_{n>=3} 1/a(n) = 2*sinh(1) + cosh(1) - 7/2.
%F A070734 Sum_{n>=3} (-1)^(n+1)/a(n) = 2*sinh(1) - cosh(1) - 1/2. (End)
%t A070734 f[n_] := If[ EvenQ[n], n!, n!/2]; Table[ f[n], {n, 3, 24}]
%o A070734 (PARI) for(n=3,20,print1((3+(-1)^n)/4*n!,","))
%Y A070734 Cf. A000142, A001710.
%K A070734 nonn,easy
%O A070734 3,1
%A A070734 Sharon Sela (sharonsela(AT)hotmail.com), May 14 2002
%E A070734 More terms from _Benoit Cloitre_, May 18 2002