A322422 Numbers k such that the sum of the first k*(k+1) primes is prime.

1, 2, 3, 11, 18, 31, 34, 49, 57, 76, 79, 84, 97, 118, 139, 140, 172, 175, 183, 184, 185, 191, 208, 218, 221, 232, 233, 247, 262, 266, 294, 313, 315, 323, 333, 334, 339, 344, 351, 361, 366, 372, 407, 413, 436, 445, 461, 473, 478, 500, 545, 546, 556, 564, 577

Offset

1,2

Links

Ray Chandler, Table of n, a(n) for n = 1..1000

Formula

A322421(n) = A322420(a(n)) = A007504(A002378(a(n))).

Mathematica

f[n_] := Sum[Prime[k], {k, n}]; Select[Range[500],
PrimeQ[f[#*(# + 1)]] &]

Crossrefs

Cf. A002378, A007504, A322420, A322421.

Sequence in context: A263938 A263932 A267420 * A024861 A025101 A025105

Adjacent sequences: A322419 A322420 A322421 * A322423 A322424 A322425

Keyword

nonn

Author

Ray Chandler, Dec 07 2018

Status

approved