OFFSET
3,4
COMMENTS
Legendre proved that a number N is the sum of five n-gonal numbers if N >= 28(n-2)^3. For odd n, four n-gonal numbers are enough. See A118368.
REFERENCES
Melvyn B. Nathanson, Additive number theory: the classical bases, Springer, 1996.
LINKS
R. K. Guy, Every number is expressible as the sum of how many polygonal numbers?, Amer. Math. Monthly 101 (1994), 169-172.
Eric Weisstein's World of Mathematics, Polygonal Number
CROSSREFS
KEYWORD
nonn
AUTHOR
T. D. Noe, Apr 25 2006
STATUS
approved