a(n) = Sum_{k=1..n} (-1)^(n+k)*A087322(n,k).

Terms

a(0) =3a(1) =6a(2) =23a(3) =50a(4) =131a(5) =294a(6) =687a(7) =1530a(8) =3419a(9) =7502a(10) =16391a(11) =35490a(12) =76467a(13) =163830a(14) =349535a(15) =742730a(16) =1572875a(17) =3320478a(18) =6990519a(19) =14680050a(20) =30758243a(21) =64312646a(22) =134217743a(23) =279620250a(24) =581610171a(25) =1207959534a(26) =2505397607a(27) =5189752130a(28) =10737418259a(29) =22190664342