A171570 Triangular numbers T such that T+2 is a prime.

1, 3, 15, 21, 45, 105, 171, 231, 351, 465, 561, 741, 861, 1275, 1431, 1485, 2211, 2415, 2775, 3081, 3321, 4005, 4371, 5151, 7875, 8385, 10731, 11175, 11781, 13041, 13695, 14535, 15051, 15225, 17205, 17391, 17955, 18915, 21321, 22155, 23871, 24531

Offset

1,2

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Example

1+2=3, 3+2=5, 15+2=17, ..

Mathematica

Select[s=0; Table[n*(n+1)/2, {n, 6!}], PrimeQ[ #+2]&]
Select[Accumulate[Range[300]], PrimeQ[#+2]&] (* Harvey P. Dale, Jun 27 2017 *)

Crossrefs

Cf. A000217, A129545, A129752, A171569.

Sequence in context: A014493 A147025 A147017 * A350987 A076825 A259745

Adjacent sequences: A171567 A171568 A171569 * A171571 A171572 A171573

Keyword

nonn

Author

Vladimir Joseph Stephan Orlovsky, Dec 11 2009

Status

approved