Principal diagonal of the convolution array A213756.

Terms

a(0) =1a(1) =14a(2) =65a(3) =214a(4) =597a(5) =1518a(6) =3649a(7) =8462a(8) =19157a(9) =42646a(10) =93777a(11) =204294a(12) =441781a(13) =949598a(14) =2030849a(15) =4324510a(16) =9174069a(17) =19397574a(18) =40893265a(19) =85981910a(20) =180353621a(21) =377485774a(22) =788527425a(23) =1644165294a(24) =3422550037a(25) =7113537398a(26) =14763947729