a(n) = Sum_{k=0..n} (k+1) * A026747(n, k).

Terms

a(0) =1a(1) =3a(2) =10a(3) =25a(4) =71a(5) =166a(6) =444a(7) =1002a(8) =2601a(9) =5742a(10) =14653a(11) =31864a(12) =80472a(13) =173077a(14) =434243a(15) =926144a(16) =2313939a(17) =4902478a(18) =12216163a(19) =25743143a(20) =64042535a(21) =134356858a(22) =333927795a(23) =697932219a(24) =1733779702a(25) =3612110059a(26) =8971527052a(27) =18639230426