A228491 Numbers k for which sum(first k primes) = 3*prime(m) for some m.

10, 16, 18, 28, 32, 34, 36, 44, 46, 54, 82, 136, 138, 246, 250, 276, 286, 362, 370, 378, 390, 554, 570, 586, 588, 668, 678, 684, 688, 690, 726, 766, 770, 826, 856, 860, 878, 880, 888, 924, 928, 932, 956, 962, 1048, 1160, 1174, 1210, 1264, 1286, 1292, 1506

Offset

1,1

Links

Table of n, a(n) for n=1..52.

Example

a(1) = 10 because 2 + 3 + 5 + ... + 29 = 3*prime(14) and p(10) = 29 is the least such prime summand.

Mathematica

z = 2800; f[n_] := Sum[Prime[k], {k, 1, n}]; p[n_] := If[PrimeQ[f[n]/3], 1, 0]; t = Table[p[n], {n, 1, z}]; Flatten[Position[t, 1]]

Crossrefs

Cf. A013916, A228490.

Sequence in context: A192221 A106695 A053747 * A295667 A241763 A233579

Adjacent sequences: A228488 A228489 A228490 * A228492 A228493 A228494

Keyword

nonn

Author

Clark Kimberling, Oct 01 2013

Status

approved