A173910 a(n) = smallest number >= a(n-1) such that a(1)*a(2)*...*a(n)+1 is prime; a(1)=2.

2, 2, 3, 3, 3, 4, 5, 7, 10, 14, 15, 18, 30, 32, 46, 56, 58, 59, 84, 86, 99, 101, 103, 106, 122, 126, 128, 128, 136, 152, 157, 170, 190, 208, 281, 282, 284, 320, 393, 406, 459, 479, 526, 529, 530, 540, 559, 601, 639, 640, 709, 789, 828, 900, 917, 949, 1029, 1029

Offset: 1

Author

Dmitry Kamenetsky, Mar 02 2010

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..700

Crossrefs

Cf. A036012, A046966.

Programs

Mathematica

a[1] = 2; a[n_] := a[n] = Module[{k = a[n - 1], r = Product[a[i], {i, 1, n - 1}]}, While[! PrimeQ[k*r + 1], k++]; k]; Array[a, 60] (* Amiram Eldar, Jan 19 2023 *)

Extensions

More terms from Amiram Eldar, Jan 19 2023