Principal diagonal of the convolution array A213576.

Terms

a(0) =1a(1) =4a(2) =17a(3) =56a(4) =172a(5) =498a(6) =1395a(7) =3820a(8) =10307a(9) =27534a(10) =73064a(11) =193012a(12) =508341a(13) =1336132a(14) =3507189a(15) =9197732a(16) =24107124a(17) =63159782a(18) =165433895a(19) =433246860a(20) =1134484871a(21) =2970509594a(22) =7777554192a(23) =20363014056a(24) =53312938537a(25) =139578241348