OFFSET
1,1
COMMENTS
It is conjectured that 1348 positive numbers are not the sum of three heptagonal numbers.
REFERENCES
R. K. Guy, Unsolved Problems in Number Theory, D3.
LINKS
T. D. Noe, Table of n, a(n) for n = 1..1348
R. K. Guy, Every number is expressible as the sum of how many polygonal numbers?, Amer. Math. Monthly 101 (1994), 169-172.
MATHEMATICA
nn = 350; hep = Table[n*(5*n-3)/2, {n, 0, nn}]; t = Table[0, {hep[[-1]]}]; Do[n = hep[[i]] + hep[[j]] + hep[[k]]; If[n <= hep[[-1]], t[[n]] = 1], {i, nn}, {j, i, nn}, {k, j, nn}]; Flatten[Position[t, 0]]
CROSSREFS
KEYWORD
nonn,fini
AUTHOR
T. D. Noe, Jul 16 2012
STATUS
approved