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A213523
Numbers not representable as the sum of three heptagonal numbers.
3
4, 5, 6, 10, 11, 12, 13, 16, 17, 22, 23, 24, 27, 28, 29, 30, 31, 33, 38, 39, 40, 44, 45, 46, 47, 49, 50, 51, 58, 60, 61, 64, 65, 66, 67, 71, 72, 76, 77, 78, 79, 84, 85, 87, 92, 93, 94, 97, 98, 101, 103, 104, 105, 108, 109, 118, 121, 124, 125, 127, 129, 132
OFFSET
1,1
COMMENTS
It is conjectured that 1348 positive numbers are not the sum of three heptagonal numbers.
REFERENCES
R. K. Guy, Unsolved Problems in Number Theory, D3.
LINKS
MATHEMATICA
nn = 350; hep = Table[n*(5*n-3)/2, {n, 0, nn}]; t = Table[0, {hep[[-1]]}]; Do[n = hep[[i]] + hep[[j]] + hep[[k]]; If[n <= hep[[-1]], t[[n]] = 1], {i, nn}, {j, i, nn}, {k, j, nn}]; Flatten[Position[t, 0]]
CROSSREFS
Cf. A000566 (heptagonal numbers).
Sequence in context: A144022 A028280 A120520 * A246441 A026312 A070751
KEYWORD
nonn,fini
AUTHOR
T. D. Noe, Jul 16 2012
STATUS
approved