Principal diagonal of the convolution array A213822.

Terms

a(0) =4a(1) =41a(2) =147a(3) =358a(4) =710a(5) =1239a(6) =1981a(7) =2972a(8) =4248a(9) =5845a(10) =7799a(11) =10146a(12) =12922a(13) =16163a(14) =19905a(15) =24184a(16) =29036a(17) =34497a(18) =40603a(19) =47390a(20) =54894a(21) =63151a(22) =72197a(23) =82068a(24) =92800a(25) =104429a(26) =116991a(27) =130522a(28) =145058a(29) =160635