A213525 Numbers not representable as the sum of three 9-gonal numbers.

4, 5, 6, 7, 8, 12, 13, 14, 15, 16, 17, 20, 21, 22, 23, 28, 29, 30, 31, 32, 35, 36, 37, 38, 39, 40, 41, 43, 44, 45, 50, 51, 52, 53, 54, 58, 59, 60, 61, 62, 63, 65, 66, 67, 68, 69, 73, 74, 78, 80, 81, 82, 83, 86, 87, 88, 89, 90, 91, 95, 96, 97, 98, 102, 103

Offset

1,1

Comments

It is conjectured that 5282 positive numbers are not the sum of three 9-gonal numbers.

References

R. K. Guy, Unsolved Problems in Number Theory, D3.

Links

T. D. Noe, Table of n, a(n) for n = 1..5282

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

Mathematica

nn = 700; non = Table[n*(7*n - 5)/2, {n, 0, nn}]; t = Table[0, {non[[-1]]}]; Do[n = non[[i]] + non[[j]] + non[[k]]; If[n <= non[[-1]], t[[n]] = 1], {i, nn}, {j, i, nn}, {k, j, nn}]; Flatten[Position[t, 0]]

Crossrefs

Cf. A001106 (9-gonal numbers).

Cf. A118278, A118279.

Sequence in context: A161428 A285429 A073073 * A047567 A050038 A285218

Adjacent sequences: A213522 A213523 A213524 * A213526 A213527 A213528

Keyword

nonn,fini

Author

T. D. Noe, Jul 16 2012

Status

approved