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A281868
Number of sets of exactly eight positive integers <= n having a square element sum.
2
1, 1, 3, 13, 34, 86, 197, 405, 786, 1446, 2532, 4263, 6938, 10953, 16837, 25281, 37165, 53605, 75999, 106075, 145951, 198199, 265921, 352825, 463320, 602609, 776797, 993007, 1259503, 1585839, 1983013, 2463629, 3042066, 3734648, 4559849, 5538527, 6694180
OFFSET
8,3
LINKS
EXAMPLE
a(8) = 1: {1,2,3,4,5,6,7,8}.
a(10) = 3: {1,2,3,4,5,6,7,8}, {1,3,5,6,7,8,9,10}, {2,3,4,6,7,8,9,10}.
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, 7), j=isqrt(n-28)..isqrt(8*n-28)))
end:
seq(a(n), n=8..60);
CROSSREFS
Column k=8 of A281871.
Sequence in context: A211801 A016061 A154154 * A137976 A095661 A058214
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Feb 01 2017
STATUS
approved