A144724 a(n) is the smallest positive integer such that b * (Product_{k=1..n} a(k)) + 1 is prime, with b = 4.

1, 3, 5, 7, 8, 9, 11, 12, 14, 17, 20, 24, 30, 34, 44, 72, 85, 86, 92, 115, 122, 125, 132, 142, 150, 161, 162, 181, 186, 198, 224, 248, 252, 282, 283, 290, 307, 319, 321, 344, 350, 376, 445, 476, 567, 623, 676, 682, 704, 741, 749, 786, 803, 806, 893, 1014, 1046, 1079

Offset: 1

Author

Artur Jasinski, Sep 19 2008

Keywords

• nonn

Comments

Is this A144717 without the 2? - R. J. Mathar, Jul 24 2023

Examples

			4*1+1=5 is prime => a(1)=1.
4*1*2+1=9 is not prime (omitted).
4*1*3+1=13 is prime => a(2)=3.
		

Crossrefs

Cf. A046966, A046972, A144717, A144718, A144722, A144723, A144725, A144726, A144727, A144728, A144729, A144730, A144731.

Programs

Mathematica

k = 4; a = {}; Do[If[PrimeQ[k n + 1], k = k n; AppendTo[a, n]], {n, 1, 3000}]; a (* Artur Jasinski *)

Extensions

Definition corrected by Georg Fischer, Jun 18 2021