A076199 a(n) equals the least s>0 such that n!! + s^2 is prime.

1, 1, 2, 3, 2, 5, 2, 5, 8, 7, 2, 19, 4, 17, 58, 11, 2, 17, 8, 31, 32, 17, 8, 13, 4, 23, 4, 23, 2, 53, 86, 37, 32, 23, 164, 79, 86, 23, 2, 229, 94, 89, 2, 89, 4, 83, 4, 149, 134, 31, 8, 83, 4, 53, 206, 227, 206, 283, 64, 43, 274, 37, 128, 263, 214, 163, 146, 167, 326, 157, 178

Offset: 1

Author

Zak Seidov, Nov 02 2002

Keywords

• nonn

Crossrefs

Cf. A057019.

Programs

Mathematica

sp[n_]:=Module[{np=NextPrime[n]},While[!IntegerQ[Sqrt[np-n]],np = NextPrime[ np]];Sqrt[np-n]]; sp/@(Range[80]!!) (* Harvey P. Dale, Aug 04 2014 *)