A228490 Numbers k for which prime(1) + ... + prime(k) = 2*prime(m) for some m.

3, 7, 55, 59, 65, 75, 93, 133, 137, 141, 249, 277, 313, 365, 375, 387, 391, 435, 471, 499, 563, 573, 597, 605, 619, 645, 675, 719, 787, 797, 799, 815, 825, 845, 867, 879, 919, 937, 957, 971, 1011, 1013, 1145, 1217, 1225, 1243, 1251, 1271, 1283, 1311, 1373

Offset

1,1

Links

Table of n, a(n) for n=1..51.

Example

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

Mathematica

z = 2800; f[n_] := Sum[Prime[k], {k, 1, n}]; p[n_] := If[PrimeQ[f[n]/2], 1, 0]; t = Table[p[n], {n, 1, z}]; Flatten[Position[t, 1]]

Crossrefs

Cf. A013916, A228491.

Sequence in context: A095124 A204254 A144030 * A130294 A321968 A100772

Adjacent sequences: A228487 A228488 A228489 * A228491 A228492 A228493

Keyword

nonn

Author

Clark Kimberling, Oct 01 2013

Status

approved