A214421 Numbers not representable as the sum of three 12-gonal numbers.

4, 5, 6, 7, 8, 9, 10, 11, 15, 16, 17, 18, 19, 20, 21, 22, 23, 26, 27, 28, 29, 30, 31, 32, 37, 38, 39, 40, 41, 42, 43, 44, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 58, 59, 60, 61, 62, 63, 68, 69, 70, 71, 72, 73, 74, 75, 79, 80, 81, 82, 83, 84, 85, 86, 87, 89

Offset

1,1

Comments

There are an infinite number of numbers that are not the sum of three 12-gonal numbers.

References

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

Links

T. D. Noe, Table of n, a(n) for n = 1..10000

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

Mathematica

nn = 100; dod = Table[n*(5n-4), {n, 0, nn}]; t = Table[0, {dod[[-1]]}]; Do[n = dod[[i]] + dod[[j]] + dod[[k]]; If[n <= dod[[-1]], t[[n]] = 1], {i, nn}, {j, i, nn}, {k, j, nn}]; Flatten[Position[t, 0]]

Crossrefs

Cf. A051624 (12-gonal numbers).

Cf. A118278, A118279.

Sequence in context: A194283 A299546 A039128 * A380974 A294237 A162706

Adjacent sequences: A214418 A214419 A214420 * A214422 A214423 A214424

Keyword

nonn

Author

T. D. Noe, Jul 17 2012

Status

approved