a(n) = binomial(9*n, n-9).A281580a(n) = binomial(9*n, n-9).Terms a(0) =1a(1) =90a(2) =4851a(3) =204156a(4) =7413705a(5) =244222650a(6) =7511839335a(7) =219683466288External referencesoeis: A281580