OFFSET
1,1
COMMENTS
7 is the only prime heptagonal number. Primes which are sums of two positive heptagonal numbers include: {2, 19, 41, 73, 89, 113, 149, 167, 193, 223, 229, 269, 293, 337, 347, 367, 383, ...}.
MATHEMATICA
Lim=348; nl=Ceiling[Sqrt[(2/5)Lim]]; Select[Union[Total/@Tuples[Table[n*(5n-3)/2, {n, nl}], {2}]], #<Lim&] (* James C. McMahon, Sep 27 2024 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Jonathan Vos Post, Apr 18 2006
EXTENSIONS
Missing 343 added by Giovanni Resta, Jun 15 2016
STATUS
approved