// output of ./demo/comb/perm-involution-demo.cc: // Description: //% Involutions (self-inverse permutations). //% Cf. OEIS sequence A000085. arg 1: 5 == n [Self-inverse permutations of n elements.] default=5 1: [ . 1 2 3 4 ] (0) (1) (2) (3) (4) 2: [ . 1 2 4 3 ] (0) (1) (2) (3, 4) 3: [ . 1 4 3 2 ] (0) (1) (2, 4) (3) 4: [ . 4 2 3 1 ] (0) (1, 4) (2) (3) 5: [ 4 1 2 3 . ] (0, 4) (1) (2) (3) 6: [ . 1 3 2 4 ] (0) (1) (2, 3) (4) 7: [ . 4 3 2 1 ] (0) (1, 4) (2, 3) 8: [ 4 1 3 2 . ] (0, 4) (1) (2, 3) 9: [ . 3 2 1 4 ] (0) (1, 3) (2) (4) 10: [ . 3 4 1 2 ] (0) (1, 3) (2, 4) 11: [ 4 3 2 1 . ] (0, 4) (1, 3) (2) 12: [ 3 1 2 . 4 ] (0, 3) (1) (2) (4) 13: [ 3 1 4 . 2 ] (0, 3) (1) (2, 4) 14: [ 3 4 2 . 1 ] (0, 3) (1, 4) (2) 15: [ . 2 1 3 4 ] (0) (1, 2) (3) (4) 16: [ . 2 1 4 3 ] (0) (1, 2) (3, 4) 17: [ 4 2 1 3 . ] (0, 4) (1, 2) (3) 18: [ 3 2 1 . 4 ] (0, 3) (1, 2) (4) 19: [ 2 1 . 3 4 ] (0, 2) (1) (3) (4) 20: [ 2 1 . 4 3 ] (0, 2) (1) (3, 4) 21: [ 2 4 . 3 1 ] (0, 2) (1, 4) (3) 22: [ 2 3 . 1 4 ] (0, 2) (1, 3) (4) 23: [ 1 . 2 3 4 ] (0, 1) (2) (3) (4) 24: [ 1 . 2 4 3 ] (0, 1) (2) (3, 4) 25: [ 1 . 4 3 2 ] (0, 1) (2, 4) (3) 26: [ 1 . 3 2 4 ] (0, 1) (2, 3) (4) ct=26