A082458 - OEIS

%I #21 Oct 24 2024 10:28:30

%S 0,0,1,2,4,12,15,60,64,320,325,1950,1956,13692,13699,109592,109600,

%T 986400,986409,9864090,9864100,108505100,108505111,1302061332,

%U 1302061344,16926797472,16926797485,236975164790,236975164804,3554627472060,3554627472075,56874039553200,56874039553216

%N Multiply by 1, add 1, multiply by 2, add 2, etc., starting with 0.

%C Bisections: A007526 and A038154.

%H Paolo Xausa, <a href="/A082458/b082458.txt">Table of n, a(n) for n = 0..800</a>

%F 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 Module[{a = 0}, Join[{a}, Flatten[Array[{a *= #, a += #} &, 20]]]] (* _Paolo Xausa_, Oct 24 2024 *)

%o (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 (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 Cf. A019464 (same, but start with 1), A019465 (start with 2), A019466 (start with 3).

%Y Cf. A019460 .. A019463 & A082448 (similar, but first add, then multiply).

%K nonn

%O 0,4

%A _Vladeta Jovovic_, Apr 25 2003

%E Edited by _M. F. Hasler_, Feb 25 2018