Diagonal sums of triangle A055249.

Terms

a(0) =1a(1) =3a(2) =9a(3) =24a(4) =61a(5) =149a(6) =354a(7) =823a(8) =1881a(9) =4240a(10) =9449a(11) =20857a(12) =45666a(13) =99291a(14) =214589a(15) =461336a(16) =987221a(17) =2103917a(18) =4467394a(19) =9454895a(20) =19951601a(21) =41989408a(22) =88155409a(23) =184670769a(24) =386072386a(25) =805624179a(26) =1678235829a(27) =3490492968a(28) =7249103581a(29) =15034563845