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 A082458 #21 Oct 24 2024 10:28:30
%S A082458 0,0,1,2,4,12,15,60,64,320,325,1950,1956,13692,13699,109592,109600,
%T A082458 986400,986409,9864090,9864100,108505100,108505111,1302061332,
%U A082458 1302061344,16926797472,16926797485,236975164790,236975164804,3554627472060,3554627472075,56874039553200,56874039553216
%N A082458 Multiply by 1, add 1, multiply by 2, add 2, etc., starting with 0.
%C A082458 Bisections: A007526 and A038154.
%H A082458 Paolo Xausa, <a href="/A082458/b082458.txt">Table of n, a(n) for n = 0..800</a>
%F A082458 For n>=2, a(2n)=floor(e*n!)-1, a(2*n+1)=(n+1)*(floor(e*n!)-1). - _Benoit Cloitre_, Apr 28 2003
%t A082458 Module[{a = 0}, Join[{a}, Flatten[Array[{a *= #, a += #} &, 20]]]] (* _Paolo Xausa_, Oct 24 2024 *)
%o A082458 (PARI) a(n)=if(n<2,0,if(n%2,(n+1)/2*(floor(exp(1)*((n-1)/2)!)-1),floor(exp(1)*(n/2)!)-1))
%o A082458 (PARI) A082458(n,a=0)={for(i=2,n+1,if(bittest(i,0),a+=i\2,a*=i\2));a} \\ _M. F. Hasler_, Feb 25 2018
%Y A082458 Cf. A019464 (same, but start with 1), A019465 (start with 2), A019466 (start with 3).
%Y A082458 Cf. A019460 .. A019463 & A082448 (similar, but first add, then multiply).
%K A082458 nonn
%O A082458 0,4
%A A082458 _Vladeta Jovovic_, Apr 25 2003
%E A082458 Edited by _M. F. Hasler_, Feb 25 2018