A281869 Number of sets of exactly nine positive integers <= n having a square element sum.

0, 1, 3, 14, 47, 121, 296, 660, 1358, 2646, 4905, 8704, 14887, 24649, 39651, 62175, 95286, 143038, 210732, 305210, 435195, 611697, 848494, 1162662, 1575195, 2111713, 2803273, 3687272, 4808464, 6220104, 7985229, 10178073, 12885638, 16209468, 20267579, 25196567

Offset: 9

Author

Alois P. Heinz, Feb 01 2017

Keywords

• nonn

Examples

			a(10) = 1: {1,2,3,4,5,7,8,9,10}.
a(11) = 3: {1,2,3,4,5,6,7,10,11}, {1,2,3,4,5,6,8,9,11}, {1,2,3,4,5,7,8,9,10}.
		

Links

• Alois P. Heinz, Table of n, a(n) for n = 9..1000

Crossrefs

Column k=9 of A281871.

Programs

Maple

b:= proc(n, i, t) option remember;
      `if`(i(t+1)*(2*i-t)/2, 0,
      `if`(i>n, 0, b(n-i, i-1, t-1))+b(n, i-1, t))))
    end:
a:= proc(n) option remember; `if`(n<0, 0, a(n-1)+add(
       b(j^2-n, n-1, 8), j=isqrt(n-36)..isqrt(9*n-36)))
    end:
seq(a(n), n=9..60);