Row sums of square of trinomial triangle A071675.

Terms

a(0) =1a(1) =1a(2) =3a(3) =9a(4) =25a(5) =69a(6) =189a(7) =519a(8) =1428a(9) =3930a(10) =10812a(11) =29742a(12) =81816a(13) =225070a(14) =619156a(15) =1703262a(16) =4685565a(17) =12889687a(18) =35458707a(19) =97544655a(20) =268339161a(21) =738183999a(22) =2030697309a(23) =5586319365a(24) =15367609920a(25) =42275319276a(26) =116296719448a(27) =319924891972a(28) =880093067016