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A281866 Number of sets of exactly six positive integers <= n having a square element sum. 2
0, 1, 3, 7, 19, 39, 74, 134, 227, 365, 568, 854, 1247, 1777, 2479, 3392, 4562, 6043, 7898, 10194, 13010, 16428, 20547, 25474, 31330, 38248, 46370, 55846, 66843, 79544, 94161, 110917, 130044, 151782, 176391, 204159, 235410, 270487, 309744, 353539, 402255 (list; graph; refs; listen; history; text; internal format)
OFFSET

6,3

LINKS

Alois P. Heinz, Table of n, a(n) for n = 6..1000

EXAMPLE

a(7) = 1: {1,2,4,5,6,7}.

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

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, 5), j=isqrt(n-15)..isqrt(6*n-15)))

    end:

seq(a(n), n=6..60);

CROSSREFS

Column k=6 of A281871.

Sequence in context: A047025 A222465 A239416 * A173114 A163572 A292775

Adjacent sequences:  A281863 A281864 A281865 * A281867 A281868 A281869

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Feb 01 2017

STATUS

approved

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Last modified February 21 23:27 EST 2019. Contains 320381 sequences. (Running on oeis4.)