Exponential convolution of A015128 with themselves.

Terms

a(0) =1a(1) =4a(2) =16a(3) =64a(4) =252a(5) =968a(6) =3616a(7) =13120a(8) =46432a(9) =160772a(10) =545856a(11) =1821056a(12) =5979520a(13) =19350552a(14) =61795968a(15) =194964672a(16) =608261628a(17) =1878140024a(18) =5743681784a(19) =17408223328a(20) =52320105080a(21) =156011658272a(22) =461763417056