Column 2 of triangle A354650: a(n) = A354650(n,2), for n >= 1.

Terms

a(0) =3a(1) =27a(2) =147a(3) =630a(4) =2295a(5) =7476a(6) =22302a(7) =62100a(8) =163260a(9) =409080a(10) =983367a(11) =2280306a(12) =5122026a(13) =11184075a(14) =23806575a(15) =49521456a(16) =100872135a(17) =201558231a(18) =395675475a(19) =764130780a(20) =1453424259a(21) =2725614243a(22) =5044092372a(23) =9219499800a(24) =16655554125a(25) =29759775435a(26) =52623867051