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A117104
Sum of two positive heptagonal numbers A000566.
2
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, ...}.
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
KEYWORD
easy,nonn
AUTHOR
Jonathan Vos Post, Apr 18 2006
EXTENSIONS
Missing 343 added by Giovanni Resta, Jun 15 2016
STATUS
approved