A084716 a(1) = 1, a(n) = smallest multiple of a(n-1) > a(n-1) such that a(n) + 1 is a prime.

1, 2, 4, 12, 36, 72, 432, 1296, 2592, 10368, 72576, 508032, 1524096, 12192768, 73156608, 146313216, 438939648, 2633637888, 23702740992, 142216445952, 1991030243328, 37829574623232, 416125320855552, 1664501283422208, 6658005133688832, 126502097540087808

Offset: 1

Author

Amarnath Murthy, Jun 11 2003

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..577

Crossrefs

Cf. A084717, A084718, A036012.

Programs

Mathematica

a[1] = 1; a[n_] := a[n] = Catch[For[k = 2, True, k++, an = k*a[n - 1]; If[PrimeQ[an + 1], Throw[an]]]]; Table[a[n], {n, 1, 23}] (* Jean-François Alcover, Nov 27 2012 *)

Extensions

Edited by Don Reble, Jun 19 2003