a(n) = Sum_{m=1..n} T(m,n+1-m), array T as in A048887.

Terms

a(0) =0a(1) =1a(2) =2a(3) =4a(4) =7a(5) =13a(6) =23a(7) =42a(8) =76a(9) =139a(10) =255a(11) =471a(12) =873a(13) =1627a(14) =3044a(15) =5718a(16) =10779a(17) =20387a(18) =38673a(19) =73561a(20) =140267a(21) =268065a(22) =513349a(23) =984910a(24) =1892874a(25) =3643569a(26) =7023561a(27) =13557019a(28) =26200181a(29) =50691977