G.f. A(x) satisfies: (1 - x*A(x))^5 = 1 - 5*x - x^5*A(x^5).

Terms

a(0) =1a(1) =2a(2) =6a(3) =21a(4) =80a(5) =320a(6) =1326a(7) =5637a(8) =24434a(9) =107542a(10) =479196a(11) =2157045a(12) =9792702a(13) =44780606a(14) =206055346a(15) =953305632a(16) =4431463863a(17) =20686696920a(18) =96931500840a(19) =455722378776