a(n) = A239839(n)/n! where A239839(n) is the number of ordered pairs of permutation functions on n elements where f(f(f(x))) = g(f(g(x))).

A255516

a(n) = A239839(n)/n! where A239839(n) is the number of ordered pairs of permutation functions on n elements where f(f(f(x))) = g(f(g(x))).

Terms

    a(0) =1a(1) =1a(2) =2a(3) =3a(4) =7a(5) =13a(6) =29a(7) =53a(8) =126a(9) =258a(10) =602a(11) =1250a(12) =3031a(13) =6703a(14) =16367a(15) =36698a(16) =91731a(17) =214315a(18) =542225a(19) =1284284a(20) =3305371a(21) =8063704a(22) =21017382a(23) =51961767a(24) =137324923a(25) =347282636a(26) =928913378a(27) =2379051372a(28) =6439629060a(29) =16796126329

External references