A048643 Differences between partial products of Gray code (A048642) and factorials (A000142).

0, 0, 1, 0, 12, 132, 540, 0, 20160, 423360, 8164800, 125193600, 1172102400, 11935123200, 76281004800, 0, 10461394944000, 428917192704000, 14781951055872000, 429147343392768000, 14090871305871360000, 461146030563778560000, 13730871481551544320000, 390084405122331279360000

Offset: 0

Author

Antti Karttunen, Jul 14 1999

Keywords

• easy
• nonn

Comments

a((2^n)-1) = 0 for all n.

Crossrefs

Cf. A000142, A048642, A048644.

Programs

PARI

a(n) = prod(i=1, n, bitxor(i, i>>1)) - n!; \\ Michel Marcus, Oct 02 2015

Formula

a(0) = 0, a(n) = product(XORnos(j, floor(j/2)), j=1..n) - n!.

a(n) = A048642(n) - A000142(n).

Extensions

More terms from Michel Marcus, Oct 02 2015