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 A244522 Number of simple involutions of length n. 1
 1, 1, 2, 0, 0, 2, 4, 10, 36, 126, 454, 1744, 6892, 28486, 120962, 531660, 2398248, 11127674, 52888998, 257570104, 1282439216 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Table of n, a(n) for n=0..20. EXAMPLE The a(7) = 10 simple involutions are: 01: [ 5 1 4 6 2 0 3 ] (0, 5) (1) (2, 4) (3, 6) 02: [ 4 1 6 3 0 5 2 ] (0, 4) (1) (2, 6) (3) (5) 03: [ 4 6 2 5 0 3 1 ] (0, 4) (1, 6) (2) (3, 5) 04: [ 5 3 6 1 4 0 2 ] (0, 5) (1, 3) (2, 6) (4) 05: [ 3 1 5 0 6 2 4 ] (0, 3) (1) (2, 5) (4, 6) 06: [ 3 5 2 0 6 1 4 ] (0, 3) (1, 5) (2) (4, 6) 07: [ 3 6 4 0 2 5 1 ] (0, 3) (1, 6) (2, 4) (5) 08: [ 2 5 0 3 6 1 4 ] (0, 2) (1, 5) (3) (4, 6) 09: [ 2 5 0 6 4 1 3 ] (0, 2) (1, 5) (3, 6) (4) 10: [ 2 4 0 6 1 5 3 ] (0, 2) (1, 4) (3, 6) (5) CROSSREFS Cf. A000085 (involutions), A111111 (simple permutations). Sequence in context: A127862 A342223 A223142 * A292945 A024690 A200728 Adjacent sequences: A244519 A244520 A244521 * A244523 A244524 A244525 KEYWORD nonn,more AUTHOR Joerg Arndt and Jay Pantone, Jul 21 2014 STATUS approved

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Last modified October 3 15:39 EDT 2023. Contains 365867 sequences. (Running on oeis4.)