Principal diagonal of the convolution array A213551.

Terms

a(0) =1a(1) =15a(2) =81a(3) =281a(4) =756a(5) =1722a(6) =3486a(7) =6462a(8) =11187a(9) =18337a(10) =28743a(11) =43407a(12) =63518a(13) =90468a(14) =125868a(15) =171564a(16) =229653a(17) =302499a(18) =392749a(19) =503349a(20) =637560a(21) =798974a(22) =991530a(23) =1219530a(24) =1487655a(25) =1800981a(26) =2164995a(27) =2585611a(28) =3069186a(29) =3622536