A126868 a(n) = (n+1)!! mod n.

0, 1, 2, 3, 3, 3, 6, 1, 6, 5, 1, 3, 8, 7, 0, 1, 13, 9, 1, 15, 0, 11, 1, 9, 0, 13, 0, 7, 17, 15, 1, 1, 0, 17, 0, 27, 6, 19, 0, 25, 9, 21, 1, 11, 0, 23, 46, 33, 0, 25, 0, 39, 30, 27, 0, 49, 0, 29, 58, 15, 50, 31, 0, 1, 0, 33, 1, 51, 0, 35, 1, 9, 27, 37, 0, 19, 0, 39, 78, 65, 0, 41, 82, 63, 0, 43

Offset

1,3

Links

Table of n, a(n) for n=1..86.

Example

n=3 (n+1)!! = 4!! = 8; (8 mod 3) = 2.
n=4 (n+1)!! = 5!! = 15; (15 mod 4) = 3.

Maple

P:=proc(n) local i, j, k, w; for i from 1 by 1 to n do k:=i+1; w:=i-1; while w>0 do k:=k*w; w:=w-2; od; j:=(k mod i); print(j); od; end: P(100);

Prog

(PARI) df(n) = prod(i=0, (n-1)\2, n - 2*i );
a(n) = df(n+1) % n; \\ Michel Marcus, Aug 22 2016

Crossrefs

Cf. A006882, A000165, A001147, A119688.

Sequence in context: A346048 A131048 A119688 * A373093 A134187 A078644

Adjacent sequences: A126865 A126866 A126867 * A126869 A126870 A126871

Keyword

easy,nonn

Author

Paolo P. Lava and Giorgio Balzarotti, Mar 16 2007

Status

approved