A214072 Least m>0 such that (2*n-1)!!+m and (2*n)!!-m are not relatively prime.

2, 8, 3, 3, 1, 3, 3, 3, 1, 3, 1, 3, 3, 3, 1, 3, 3, 3, 3, 3, 1, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 1, 3, 1, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 1, 3, 3, 3, 3, 3, 3, 3, 3, 3, 1, 3, 3, 3, 3, 3, 1, 3, 1, 3, 3, 3, 3, 3, 1, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3

Offset

1,1

Links

Clark Kimberling, Table of n, a(n) for n = 1..1000

Example

gcd(15+1,48-1) = 1, gcd(15+2,48-2) = 1, gcd(15+3,48-3) > 1, so that a(3) = 3.

Mathematica

b[n_] := (2 n - 1)!!; c[n_] := (2 n)!!;
Table[m = 1; While[GCD[b[n] + m, c[n] - m] == 1, m++]; m, {n, 1, 140}]

Crossrefs

Cf. A214054.

Sequence in context: A273692 A006085 A021357 * A016640 A321984 A083486

Adjacent sequences: A214069 A214070 A214071 * A214073 A214074 A214075

Keyword

nonn,easy

Author

Clark Kimberling, Jul 26 2012

Status

approved