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A193774 Number of signed permutations of length n invariant under the reverse complement and avoiding (-2, 1) and (2, -1). 0
1, 2, 4, 6, 20, 26, 124, 146, 956, 1050, 9100 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..10.

EXAMPLE

For n = 2, the permutations are (1, 2), (2, 1), (-1, -2), and (-2, -1).

CROSSREFS

Sequence in context: A279188 A108439 A245766 * A241210 A333992 A176652

Adjacent sequences:  A193771 A193772 A193773 * A193775 A193776 A193777

KEYWORD

nonn

AUTHOR

Andy Hardt, Aug 04 2011

STATUS

approved

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Last modified August 19 23:59 EDT 2022. Contains 356231 sequences. (Running on oeis4.)