A213523 Numbers not representable as the sum of three heptagonal numbers.

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

T. D. Noe, Table of n, a(n) for n = 1..1348

R. K. Guy, Every number is expressible as the sum of how many polygonal numbers?, Amer. Math. Monthly 101 (1994), 169-172.

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).

Cf. A118278, A118279.

Sequence in context: A144022 A028280 A120520 * A246441 A026312 A070751

Adjacent sequences: A213520 A213521 A213522 * A213524 A213525 A213526

Keyword

nonn,fini

Author

T. D. Noe, Jul 16 2012

Status

approved