a(n+1) = 2*n*a(n) + 2 with a(0)=1.

Terms

a(0) =1a(1) =2a(2) =6a(3) =26a(4) =158a(5) =1266a(6) =12662a(7) =151946a(8) =2127246a(9) =34035938a(10) =612646886a(11) =12252937722a(12) =269564629886