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A286815
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Square array A(n,k), n>=0, k>=0, read by antidiagonals, where column k is the expansion of (Product_{j>=1} (1 - x^(2*j))^5/((1 - x^j)*(1 - x^(4*j)))^2)^k.
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26
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1, 1, 0, 1, 2, 0, 1, 4, 0, 0, 1, 6, 4, 0, 0, 1, 8, 12, 0, 2, 0, 1, 10, 24, 8, 4, 0, 0, 1, 12, 40, 32, 6, 8, 0, 0, 1, 14, 60, 80, 24, 24, 0, 0, 0, 1, 16, 84, 160, 90, 48, 24, 0, 0, 0, 1, 18, 112, 280, 252, 112, 96, 0, 4, 2, 0, 1, 20, 144, 448, 574, 312, 240, 64, 12
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OFFSET
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0,5
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COMMENTS
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A(n,k) is the number of ways of writing n as a sum of k squares.
This is the transpose of the array in A122141.
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LINKS
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FORMULA
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G.f. of column k: (Product_{j>=1} (1 - x^(2*j))^5/((1 - x^j)*(1 - x^(4*j)))^2)^k.
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EXAMPLE
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Square array begins:
1, 1, 1, 1, 1, ...
0, 2, 4, 6, 8, ...
0, 0, 4, 12, 24, ...
0, 0, 0, 8, 32, ...
0, 2, 4, 6, 24, ...
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MAPLE
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A:= proc(n, k) option remember; `if`(n=0, 1, `if`(n<0 or k<1, 0,
A(n, k-1) +2*add(A(n-j^2, k-1), j=1..isqrt(n))))
end:
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MATHEMATICA
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A[n_, k_] := A[n, k] = If[n == 0, 1, If[n < 0 || k < 1, 0, A[n, k-1] + 2*Sum[A[n-j^2, k-1], {j, 1, Sqrt[n]}]]];
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CROSSREFS
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Columns k=0-16 give: A000007, A000122, A004018, A005875, A000118, A000132, A000141, A008451, A000143, A008452, A000144, A008453, A000145, A276285, A276286, A276287, A000152.
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KEYWORD
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AUTHOR
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STATUS
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approved
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