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A117104
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Sum of two positive heptagonal numbers A000566.
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2
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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, 347
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Gauss discovered and Fermat and Legendre proved that every integer is the sum of 7 heptagonal numbers. 7 is the only prime heptagonal number. Primes which are sums of two positive heptagonal numbers include: {19, 41, 73, 89, 113, 149, 167, 193, 223, 229, 269, 293, 337, 347, 367, 383, 521, ...}.
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FORMULA
| {a(n)} = {A000566} + {A000566} = {a*(5*a-3)/2 + b*(5*b-3)/2} \ {A000566}.
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CROSSREFS
| Cf. A000566, A000040, A000326, A003679, A064826, A117065.
Sequence in context: A056715 A160556 A105610 * A082933 A016933 A101959
Adjacent sequences: A117101 A117102 A117103 * A117105 A117106 A117107
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KEYWORD
| easy,nonn
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AUTHOR
| Jonathan Vos Post (jvospost3(AT)gmail.com), Apr 18 2006
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