A048642 Partial products of A003188 (Gray code).
1, 1, 3, 6, 36, 252, 1260, 5040, 60480, 786240, 11793600, 165110400, 1651104000, 18162144000, 163459296000, 1307674368000, 31384184832000, 784604620800000, 21184324761600000, 550792443801600000, 16523773314048000000
Offset: 0
Links
- Harvey P. Dale, Table of n, a(n) for n = 0..444
Programs
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Mathematica
Join[{1},FoldList[Times,Table[BitXor[n,Floor[n/2]],{n,20}]]] (* Harvey P. Dale, Oct 05 2016 *) -
PARI
a(n) = prod(i=1, n, bitxor(i, i>>1)); \\ Michel Marcus, Apr 22 2013, Oct 02 2015
Formula
a(0) = 1, a(n) = product(XOR(j, floor(j/2)), j=1..n).
a((2^n)-1) = A000142((2^n)-1) for all n.