Number of permutations of [n] whose longest block is of length 2. A block of a permutation is a maximal sequence of consecutive integers which appear in consecutive positions.

A370390

Number of permutations of [n] whose longest block is of length 2. A block of a permutation is a maximal sequence of consecutive integers which appear in consecutive positions.

Terms

    a(0) =0a(1) =0a(2) =1a(3) =2a(4) =10a(5) =53a(6) =334a(7) =2428a(8) =20009a(9) =184440a(10) =1881050a(11) =21034905a(12) =255967940a(13) =3367720736a(14) =47641219569a(15) =721160081974

External references