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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

Harvey P. Dale, Table of n, a(n) for n = 0..444

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

Cf. A000142, A003188.

Sequence in context: A211895 A240986 A120595 * A264702 A077532 A174666

Adjacent sequences:  A048639 A048640 A048641 * A048643 A048644 A048645

KEYWORD

easy,nonn

AUTHOR

Antti Karttunen, Jul 14 1999

STATUS

approved

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Last modified February 23 18:13 EST 2019. Contains 320437 sequences. (Running on oeis4.)