a(n) is the number of compositions of the set {1, 2, ..., n} into blocks, each of size 1, 2 or 3 (n >= 0).

A189886

a(n) is the number of compositions of the set {1, 2, ..., n} into blocks, each of size 1, 2 or 3 (n >= 0).

Terms

    a(0) =1a(1) =1a(2) =3a(3) =13a(4) =74a(5) =530a(6) =4550a(7) =45570a(8) =521640a(9) =6717480a(10) =96117000a(11) =1512819000a(12) =25975395600a(13) =483169486800

External references