A073687 - OEIS

A073687

Group the composite numbers so that the sum of each group is a prime: (4, 6, 8, 9, 10), (12, 14, 15), (16, 18, 20, 21, 22), (24, 25, 26, 27, 28, 30, 32, 33, 34, 35, 36, 38, 39, 40, 42, 44, 45, 46, 48, 49, 50, 51, 52, 54, 55), ...; sequence gives first term in each group.

4, 12, 16, 24, 56, 58, 65, 68, 70, 77, 87, 94, 99, 102, 106, 114, 116, 118, 140, 142, 185, 195, 219, 221, 224, 226, 235, 255, 259, 266, 278, 280, 290, 302, 310, 318, 334, 366, 370, 375, 377, 399, 403, 411, 413, 415, 442, 447, 462, 494, 530, 532, 550, 568, 575

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OFFSET

1,1

LINKS

Table of n, a(n) for n=1..55.

MATHEMATICA

t1 = Rest[Select[Range[580], ! PrimeQ[#] &]]; t = {}; s = c = 0; Do[s += i; c += 1; If[PrimeQ[s], AppendTo[t, t1[[Flatten[Position[t1, i]] - c + 1]]]; s = c = 0], {i, t1}]; Flatten[t] (* Jayanta Basu, Jul 07 2013 *)

CROSSREFS

Cf. A073685, A073686.

Sequence in context: A261958 A057962 A186303 * A187084 A090818 A075191

Adjacent sequences: A073684 A073685 A073686 * A073688 A073689 A073690

KEYWORD

nonn

AUTHOR

Amarnath Murthy, Aug 11 2002

EXTENSIONS

More terms from Lior Manor Aug 13 2002

STATUS

approved