This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A117104 #12 Sep 27 2024 20:55:42
%S A117104 2,8,14,19,25,35,36,41,52,56,62,68,73,82,88,89,99,110,113,115,119,130,
%T A117104 136,146,149,155,162,166,167,182,190,193,196,203,207,223,224,229,236,
%U A117104 242,244,253,260,269,270,287,290,293,296,301,304,316,320,337,341,343,347
%N A117104 Sum of two positive heptagonal numbers A000566.
%C A117104 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, ...}.
%F A117104 {a(n)} = {A000566} + {A000566} = {a*(5*a-3)/2 + b*(5*b-3)/2} \ {A000566}.
%t A117104 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 *)
%Y A117104 Cf. A000566, A000040, A000326, A003679, A064826, A117065.
%K A117104 easy,nonn
%O A117104 1,1
%A A117104 _Jonathan Vos Post_, Apr 18 2006
%E A117104 Missing 343 added by _Giovanni Resta_, Jun 15 2016