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

1,2

Links

Table of n, a(n) for n=1..7.

Wikipedia, Hexagonal number.

Index to sequences related to polygonal numbers

Example

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

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]

Crossrefs

Subsequence of A175133.

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

Sequence in context: A263174 A123591 A133381 * A236066 A151589 A243114

Adjacent sequences: A366267 A366268 A366269 * A366271 A366272 A366273

Keyword

nonn,hard,more

Author

Paolo Xausa, Oct 06 2023

Status

approved