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

4, 5, 5, 7, 14, 17, 51, 55, 220, 225, 1125, 1131, 6786, 6793, 47551, 47559, 380472, 380481, 3424329, 3424339, 34243390, 34243401, 376677411, 376677423, 4520129076, 4520129089, 58761678157, 58761678171, 822663494394, 822663494409, 12339952416135, 12339952416151, 197439238658416

Offset

0,1

Links

Table of n, a(n) for n=0..32.

Nick Hobson, Python program for this sequence

Formula

For n>=2, a(2n)=floor((2e+4)*n!)-n-2, a(2n+1)=floor((2e+4)*n!)-1.

Mathematica

k = 0; NestList[(k++; {Last@# + k, k(k + Last@#)}) &, {4}, 16] // Flatten

Prog

(PARI) a=4; for(n=1, 150, print(a, ", "); b=if(n%2-1, a*ceil(n/2), a+ceil(n/2)); a=b)
(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

Crossrefs

Cf. A019461 (same, but start with 0), A019463 (start with 1), A019460 (start with 2), A019462 (start with 3).

Cf. A082458, A019464 .. A019466 (similar, but first multiply, then add).

Sequence in context: A178131 A071570 A336047 * A190796 A070783 A198334

Adjacent sequences: A082445 A082446 A082447 * A082449 A082450 A082451

Keyword

nonn,easy

Author

N. J. A. Sloane, based on a suggestion of Nick MacDonald, Apr 25 2003

Extensions

More terms from Benoit Cloitre, Apr 26 2003

Edited by M. F. Hasler, Feb 25 2018

Status

approved