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A321629
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The Riordan square of the permutation involutions. Triangle T(n, k), 0 <= k <= n, read by rows.
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1
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1, 1, 1, 2, 3, 1, 4, 8, 5, 1, 10, 22, 18, 7, 1, 26, 62, 60, 32, 9, 1, 76, 184, 194, 126, 50, 11, 1, 232, 568, 630, 462, 228, 72, 13, 1, 764, 1840, 2072, 1644, 938, 374, 98, 15, 1, 2620, 6204, 6972, 5788, 3650, 1710, 572, 128, 17, 1
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OFFSET
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0,4
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COMMENTS
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The Riordan square is defined in A321620.
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LINKS
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EXAMPLE
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[0] 1;
[1] 1, 1;
[2] 2, 3, 1;
[3] 4, 8, 5, 1;
[4] 10, 22, 18, 7, 1;
[5] 26, 62, 60, 32, 9, 1;
[6] 76, 184, 194, 126, 50, 11, 1;
[7] 232, 568, 630, 462, 228, 72, 13, 1;
[8] 764, 1840, 2072, 1644, 938, 374, 98, 15, 1;
[9] 2620, 6204, 6972, 5788, 3650, 1710, 572, 128, 17, 1;
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MAPLE
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# The function RiordanSquare is defined in A321620.
cf := proc(dim) local k, m; m := 1;
for k from dim by -1 to 1 do m := 1 - k*x - k*x^2/m od;
1/m end: RiordanSquare(cf(9), 9);
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CROSSREFS
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First column are the self-inverse permutations A000085.
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KEYWORD
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AUTHOR
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STATUS
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approved
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