A073689 Group the natural numbers so that the product of the terms in each group + 1 is a prime: (1), (2), (3, 4), (5, 6), (7, 8, 9, 10, 11), (12), (13, 14, 15), (16), ... Sequence gives first term in each group.

1, 2, 3, 5, 7, 12, 13, 16, 17, 19, 24, 26, 32, 39, 44, 47, 56, 59, 61, 64, 69, 71, 73, 78, 79, 85, 95, 108, 109, 120, 128, 131, 133, 136, 137, 144, 151, 169, 212, 219, 225, 232, 233, 260, 276, 277, 284, 290, 292, 293, 295, 311, 317, 326, 329, 331, 355, 358, 359, 365

Offset

0,2

Comments

a(k+1) - a(k) = 4 has no solution.

Links

Table of n, a(n) for n=0..59.

Mathematica

t = {}; s = 1; c = 0; Do[s = s*i; c += 1; If[PrimeQ[s + 1], AppendTo[t, i - c + 1]; s = 1; c = 0], {i, 375}]; t (* Jayanta Basu, Jul 07 2013 *)

Crossrefs

Cf. A073688, A073690.

Sequence in context: A028842 A260181 A140971 * A257560 A187774 A031216

Adjacent sequences: A073686 A073687 A073688 * A073690 A073691 A073692

Keyword

nonn

Author

Amarnath Murthy, Aug 12 2002

Extensions

More terms from Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Apr 24 2003

Status

approved