login
A213525
Numbers not representable as the sum of three 9-gonal numbers.
2
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
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).
Sequence in context: A161428 A285429 A073073 * A047567 A050038 A285218
KEYWORD
nonn,fini
AUTHOR
T. D. Noe, Jul 16 2012
STATUS
approved