Second diagonal of triangle in A145879.

Terms

a(0) =1a(1) =8a(2) =46a(3) =232a(4) =1093a(5) =4944a(6) =21778a(7) =94184a(8) =401930a(9) =1698160a(10) =7119516a(11) =29666704a(12) =123012781a(13) =508019104a(14) =2091005866a(15) =8582372584a(16) =35141476126a(17) =143595498544a(18) =585720020356