Basis for code in A075931.

Terms

a(0) =31a(1) =227a(2) =805a(3) =1354a(4) =6182a(5) =10315a(6) =18731a(7) =35149a(8) =67943a(9) =393255a(10) =655433a(11) =1181959a(12) =6291497a(13) =10485837a(14) =18874658a(15) =35653635a(16) =69337155a(17) =136446255a(18) =270666054a(19) =1610612779a(20) =2684354638a(21) =4831838504a(22) =9126807585a(23) =17716871269a(24) =34896740609