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A215456
a(n)=(4n-1)!! modulo 2n, n=1,2,...
2
1, 1, 3, 1, 5, 9, 7, 1, 9, 5, 11, 9, 13, 21, 15, 1, 17, 9, 19, 25, 21, 33, 23, 33, 25, 13, 27, 49, 29, 45, 31, 1, 33, 17, 35, 9, 37, 57, 39, 65, 41, 21, 43, 33, 45, 69, 47, 33, 49, 25, 51, 65, 53, 81, 55, 49, 57, 29, 59, 105, 61, 93, 63, 1, 65, 33, 67, 17, 69
OFFSET
1,3
COMMENTS
a(n)=1 for n = 2^k. Do all odd integers appear in the sequence?
Note some linear patterns in the graph.
Note that A001147(m) modulo m is 0 for odd m's, hence we here consider only even m's.
FORMULA
a(n)=A001147(2n) modulo 2n, n=1,2,...
MATHEMATICA
Table[Mod[(4n-1)!!, 2n], {n, 70}] (* Harvey P. Dale, Mar 29 2022 *)
CROSSREFS
Cf. A001147.
Sequence in context: A221446 A029723 A187370 * A225855 A201751 A202504
KEYWORD
nonn
AUTHOR
Zak Seidov, Aug 11 2012
STATUS
approved