

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.


2



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
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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



