Principal diagonal of the convolution array A213579.

Terms

a(0) =1a(1) =5a(2) =15a(3) =35a(4) =74a(5) =146a(6) =277a(7) =511a(8) =925a(9) =1651a(10) =2916a(11) =5108a(12) =8889a(13) =15385a(14) =26507a(15) =45491a(16) =77806a(17) =132678a(18) =225645a(19) =382835a(20) =648121a(21) =1095075a(22) =1846920a(23) =3109800a(24) =5228209a(25) =8777261a(26) =14716167a(27) =24643331a(28) =41220050a(29) =68873786