Numbers that are not the sum of 3 generalized 8-gonal numbers.
4, 12, 19, 20, 28, 36, 44, 51, 52, 60, 68, 76, 79, 83, 84, 92, 100, 108, 115, 116, 124, 132, 140, 147, 148, 156, 164, 172, 179, 180, 188, 196, 204, 207, 211, 212, 220, 228, 236, 243, 244, 252, 260, 268, 275, 276, 284, 292, 300, 307, 308, 316, 319, 324, 332
1
This table of numbers appears linear, but it is not quite so.
T. D. Noe, Plot of 1000 terms
T. D. Noe, Table of 1000 terms
Eric W. Weisstein, MathWorld: Polygonal Number
(Mma) f = 8; nn = 50; t = Table[k ((f - 2) k - (f - 4))/2, {k, -nn, nn}]; t2 = Select[Union[Flatten[Table[a + b + c, {a, t}, {b, t}, {c, t}]]], # <= t[[-1]] &]; Complement[Range[t[[-1]]], t2]
nonn
T. D. Noe, Dec 28 2015