A322058 - OEIS

A322058

Irregular triangle read by rows: T(n,k) = number of 1324-avoiding permutations of length n >= 0 having k >= 0 inversions.

1, 1, 1, 1, 1, 2, 2, 1, 1, 2, 5, 6, 5, 3, 1, 1, 2, 5, 10, 16, 20, 20, 15, 9, 4, 1, 1, 2, 5, 10, 20, 32, 51, 67, 79, 80, 68, 49, 29, 14, 5, 1, 1, 2, 5, 10, 20, 36, 61, 96, 148, 208, 268, 321, 351, 347, 308, 241, 165, 98, 49, 20, 6, 1, 1, 2, 5, 10, 20, 36, 65, 106, 171, 262, 397, 568, 784, 1019, 1264, 1478, 1628, 1681, 1619, 1441, 1173, 866, 574, 338, 174, 76, 27, 7, 1

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,6

REFERENCES

Miklos Bona, editor, Handbook of Enumerative Combinatorics, CRC Press, 2015, page 769, Fig. 12.13.

LINKS

Table of n, a(n) for n=0..92.

EXAMPLE

Triangle begins:

1, 1;

1, 2, 2, 1;

1, 2, 5, 6, 5, 3, 1;