OFFSET
1,3
COMMENTS
These are the triangular numbers n(n+1)/2 where n is not congruent to 3 or 4 mod 8. (Since the numbers not the difference of two squares are precisely those congruent to 2 mod 4.) - Franklin T. Adams-Watters, Jun 14 2007
FORMULA
G.f. ( -x^2*(x^2+1)*(x^8+2*x^7+11*x^6+4*x^5-4*x^4+4*x^3+11*x^2+2*x+1) ) / ( (1+x)^2*(1+x+x^2)^2*(x^2-x+1)^2*(x-1)^3 ) with a(n) = +a(n-1) +2*a(n-6) -2*a(n-7) -a(n-12) +a(n-13). - R. J. Mathar, Oct 25 2011
MATHEMATICA
With[{n = 100}, Intersection[(#1*((#1 + 1)/2) & ) /@ Range[0, n], Flatten[Outer[ #1^2 - #2^2 &, Range[n], Range[0, n - 1]]]]]
CROSSREFS
KEYWORD
nonn
AUTHOR
Peter Pein (petsie(AT)dordos.net), Jun 14 2007
STATUS
approved