A214586 Numbers k such that gcd(k!!+1,k-1) = 1.

2, 6, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 50, 52, 54, 56, 58, 62, 64, 66, 68, 70, 72, 74, 76, 78, 82, 86, 88, 90, 92, 94, 96, 98, 100, 102, 106, 110, 112, 114, 116, 118, 120, 122, 124, 126

Offset

1,1

Comments

Positions of 2 in A214054; complement of A214585.

Links

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

Mathematica

b[n_]:=n!!; c[n_]:=n;
t=Table[m=1; While[GCD[b[n]+m, c[n]-m]==1, m++]; m, {n, 1, 200}] (* A214054 *)
Flatten[Position[t, 1]] (* A214585 *)
Flatten[Position[t, 2]] (* A214586 *)
Select[Range[150], CoprimeQ[#!!+1, #-1]&] (* Harvey P. Dale, Dec 13 2014 *)

Crossrefs

Cf. A214054, A214585.

Sequence in context: A099017 A298748 A139799 * A337687 A305634 A139710

Adjacent sequences: A214583 A214584 A214585 * A214587 A214588 A214589

Keyword

nonn

Author

Clark Kimberling, Jul 21 2012

Status

approved