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A264466
Number of permutations of [n] with exactly seven (possibly overlapping) occurrences of the generalized pattern 23-1.
2
1, 111, 2141, 29066, 336137, 3663730, 39037155, 414003430, 4414401391, 47606401475, 521147444815, 5804080039932, 65854473968668, 761861585833395, 8990938684395442, 108258685340444377, 1330041483208589743, 16671576238569453924, 213169773223813966680
OFFSET
6,2
LINKS
EXAMPLE
a(6) = 1: 456231.
a(7) = 111: 1567342, 2456713, 2456731, ..., 6753412, 6753421, 7456231.
MAPLE
b:= proc(u, o) option remember; `if`(u+o=0, 1, add(
b(u-j, o+j-1), j=1..u) +add(convert(series(
b(u+j-1, o-j)*x^u, x, 8), polynom), j=1..o))
end:
a:= n-> coeff(b(n, 0), x, 7):
seq(a(n), n=6..25);
CROSSREFS
Column k=7 of A260670.
Sequence in context: A101152 A250145 A075859 * A302384 A303105 A008396
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Nov 14 2015
STATUS
approved