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A321629 The Riordan square of the permutation involutions. Triangle T(n, k), 0 <= k <= n, read by rows. 1
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 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

The Riordan square is defined in A321620.

LINKS

Table of n, a(n) for n=0..54.

EXAMPLE

[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;

MAPLE

# 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);

CROSSREFS

First column are the self-inverse permutations A000085.

Row sums are A193777, alternating row sums are A000007.

Cf. A321620.

Sequence in context: A118800 A200139 A321621 * A075297 A057597 A226392

Adjacent sequences:  A321626 A321627 A321628 * A321630 A321631 A321632

KEYWORD

nonn,tabl

AUTHOR

Peter Luschny, Dec 09 2018

STATUS

approved

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Last modified June 4 01:54 EDT 2020. Contains 334812 sequences. (Running on oeis4.)