A214585 Numbers k such that gcd(k!!+1,k-1) > 1.

1, 3, 4, 5, 7, 8, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 48, 49, 51, 53, 55, 57, 59, 60, 61, 63, 65, 67, 69, 71, 73, 75, 77, 79, 80, 81, 83, 84, 85, 87, 89, 91, 93, 95, 97, 99, 101, 103, 104, 105

Offset

1,2

Comments

Positions of 1 in A214054; complement of A214586.

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[120], GCD[#!!+1, #-1]>1&] (* Harvey P. Dale, Aug 06 2019 *)

Crossrefs

Cf. A214054, A214586.

Sequence in context: A330565 A139711 A354994 * A196036 A341416 A081376

Adjacent sequences: A214582 A214583 A214584 * A214586 A214587 A214588

Keyword

nonn

Author

Clark Kimberling, Jul 21 2012

Status

approved