a(n) = Sum_{0<=j<=i<=n} A027144(i, j).

Terms

a(0) =1a(1) =4a(2) =11a(3) =32a(4) =77a(5) =212a(6) =503a(7) =1376a(8) =3257a(9) =8900a(10) =21059a(11) =57536a(12) =136133a(13) =371924a(14) =879983a(15) =2404160a(16) =5688305a(17) =15540740a(18) =36769787a(19) =100456928a(20) =237683645a(21) =649363796a(22) =1536411239a(23) =4197553568a(24) =9931518377a(25) =27133412804a(26) =64198343987