Diagonal sums of A004248.

Terms

a(0) =1a(1) =0a(2) =1a(3) =1a(4) =2a(5) =3a(6) =6a(7) =12a(8) =27a(9) =64a(10) =163a(11) =441a(12) =1268a(13) =3855a(14) =12344a(15) =41464a(16) =145653a(17) =533736a(18) =2036149a(19) =8071785a(20) =33192790a(21) =141351715a(22) =622384730a(23) =2829417276a(24) =13263528351a(25) =64038928728a(26) =318121600695