a(n) = T(3*n + 1, n + 1), array T as in A038792.

Terms

a(0) =1a(1) =4a(2) =23a(3) =141a(4) =888a(5) =5676a(6) =36622a(7) =237821a(8) =1551727a(9) =10161409a(10) =66732392a(11) =439267525a(12) =2897064773a(13) =19137833146a(14) =126599140313a(15) =838477244705