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A220692
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Square array A220691 transposed.
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2
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0, 1, 0, 3, 0, 0, 6, 1, 1, 0, 10, 2, 1, 0, 0, 15, 4, 2, 1, 0, 0, 21, 6, 4, 1, 1, 0, 0, 28, 9, 5, 2, 2, 0, 0, 0, 36, 12, 7, 3, 2, 1, 0, 0, 0, 45, 16, 10, 5, 3, 2, 1, 0, 0, 0, 55, 20, 12, 6, 4, 2, 2, 0, 0, 0, 0, 66, 25, 15, 8, 6, 3, 3, 1, 0, 0, 0, 0
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OFFSET
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1,4
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LINKS
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FORMULA
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a(n) = A220691bi(A004736(n),A002260(n)). (As a sequence. As an array this is the transpose of the square array given in A220691).
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MATHEMATICA
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a[n_, 1] := n*(n-1)/2; a[n_, k_] := Module[{r}, r = Reduce[1 <= i < j <= n && Mod[i+j, k] == 0, {i, j}, Integers]; Which[Head[r] === Or, Length[r], Head[r] === And, 1, r === False, 0, True, Print[r, " not parsed"]]]; Table[a[n-k+1, k], {n, 1, 13} , {k, 1, n}] // Flatten (* Jean-François Alcover, Mar 04 2014 *)
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PROG
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CROSSREFS
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KEYWORD
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AUTHOR
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STATUS
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approved
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