A366270 Nonnegative integers k such that the sum of the first k primes is a hexagonal number.

0, 5, 93448, 39545957, 240439822, 1894541497, 132563927578

Offset: 1

Author

Paolo Xausa, Oct 06 2023

Keywords

• nonn
• hard
• more

Examples

			5 is a term because the sum of the first five primes (2 + 3 + 5 + 7 + 11 = 28) is a hexagonal number.
		

Links

• Wikipedia, Hexagonal number.
• Index to sequences related to polygonal numbers

Crossrefs

Subsequence of A175133.

Cf. A000384, A007504, A033997, A364695, A364696, A366269 (corresponding hexagonal numbers).

Programs

Mathematica

A366270list[kmax_]:=Module[{p=0},Join[{0},Table[If[IntegerQ[(Sqrt[8(p+=Prime[k])+1]+1)/4],k,Nothing],{k,kmax}]]];A366270list[10^5]