a(n) = A000203(A251720(n)).

Terms

a(0) =28a(1) =78a(2) =248a(3) =684a(4) =1862a(5) =3294a(6) =6140a(7) =9144a(8) =16590a(9) =27872a(10) =37734a(11) =59094a(12) =75812a(13) =90864a(14) =121878a(15) =171780a(16) =219542a(17) =257244a(18) =328104a(19) =378362a(20) =432240a(21) =530964a(22) =627570a(23) =785078a(24) =969714a(25) =1071512a(26) =1157004a(27) =1271270a(28) =1366974a(29) =1649024