|
|
A048642
|
|
Partial products of A003188 (Gray code).
|
|
3
|
|
|
1, 1, 3, 6, 36, 252, 1260, 5040, 60480, 786240, 11793600, 165110400, 1651104000, 18162144000, 163459296000, 1307674368000, 31384184832000, 784604620800000, 21184324761600000, 550792443801600000, 16523773314048000000
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,3
|
|
LINKS
|
|
|
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.
|
|
MATHEMATICA
|
Join[{1}, FoldList[Times, Table[BitXor[n, Floor[n/2]], {n, 20}]]] (* Harvey P. Dale, Oct 05 2016 *)
|
|
PROG
|
(PARI) a(n) = prod(i=1, n, bitxor(i, i>>1)); \\ Michel Marcus, Apr 22 2013, Oct 02 2015
|
|
CROSSREFS
|
|
|
KEYWORD
|
easy,nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|