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 A214421 Numbers not representable as the sum of three 12-gonal numbers. 2
 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 (list; graph; refs; listen; history; text; internal format)
 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 * A294237 A162706 A088331 Adjacent sequences:  A214418 A214419 A214420 * A214422 A214423 A214424 KEYWORD nonn AUTHOR T. D. Noe, Jul 17 2012 STATUS approved

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Last modified August 9 18:55 EDT 2022. Contains 356026 sequences. (Running on oeis4.)