A117104 Sum of two positive heptagonal numbers A000566.

2, 8, 14, 19, 25, 35, 36, 41, 52, 56, 62, 68, 73, 82, 88, 89, 99, 110, 113, 115, 119, 130, 136, 146, 149, 155, 162, 166, 167, 182, 190, 193, 196, 203, 207, 223, 224, 229, 236, 242, 244, 253, 260, 269, 270, 287, 290, 293, 296, 301, 304, 316, 320, 337, 341, 343, 347

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, ...}.

Links

Table of n, a(n) for n=1..57.

Formula

{a(n)} = {A000566} + {A000566} = {a*(5*a-3)/2 + b*(5*b-3)/2} \ {A000566}.

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

Cf. A000566, A000040, A000326, A003679, A064826, A117065.

Sequence in context: A160556 A105610 A324691 * A082933 A353466 A016933

Adjacent sequences: A117101 A117102 A117103 * A117105 A117106 A117107

Keyword

easy,nonn

Author

Jonathan Vos Post, Apr 18 2006

Extensions

Missing 343 added by Giovanni Resta, Jun 15 2016

Status

approved