cp's OEIS Frontend

A082448 Add 1, multiply by 1, add 2, multiply by 2, etc.; start with 4.

%I A082448 #18 Feb 25 2018 22:59:38
%S A082448 4,5,5,7,14,17,51,55,220,225,1125,1131,6786,6793,47551,47559,380472,
%T A082448 380481,3424329,3424339,34243390,34243401,376677411,376677423,
%U A082448 4520129076,4520129089,58761678157,58761678171,822663494394,822663494409,12339952416135,12339952416151,197439238658416
%N A082448 Add 1, multiply by 1, add 2, multiply by 2, etc.; start with 4.
%H A082448 Nick Hobson, <a href="/A082448/a082448.py.txt">Python program for this sequence</a>
%F A082448 For n>=2, a(2n)=floor((2e+4)*n!)-n-2, a(2n+1)=floor((2e+4)*n!)-1.
%t A082448 k = 0; NestList[(k++; {Last@# + k, k(k + Last@#)}) &, {4}, 16] // Flatten
%o A082448 (PARI) a=4; for(n=1,150,print(a,","); b=if(n%2-1,a*ceil(n/2),a+ceil(n/2)); a=b)
%o A082448 (PARI) A082448(n,a=4)={for(i=2,n+1,if(bittest(i,0),a*=i\2,a+=i\2));a} \\ _M. F. Hasler_, Feb 25 2018
%Y A082448 Cf. A019461 (same, but start with 0), A019463 (start with 1), A019460 (start with 2), A019462 (start with 3).
%Y A082448 Cf. A082458, A019464 .. A019466 (similar, but first multiply, then add).
%K A082448 nonn,easy
%O A082448 0,1
%A A082448 _N. J. A. Sloane_, based on a suggestion of Nick MacDonald, Apr 25 2003
%E A082448 More terms from _Benoit Cloitre_, Apr 26 2003
%E A082448 Edited by _M. F. Hasler_, Feb 25 2018