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A281869
Number of sets of exactly nine positive integers <= n having a square element sum.
2
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
9,3
LINKS
EXAMPLE
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}.
MAPLE
b:= proc(n, i, t) option remember;
`if`(i<t, 0, `if`(n=0, `if`(t=0, 1, 0),
`if`(t<1 or n<t*(t+1)/2 or n>(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);
CROSSREFS
Column k=9 of A281871.
Sequence in context: A027953 A264501 A104196 * A202144 A287426 A246149
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Feb 01 2017
STATUS
approved