Construct triangle in which n-th row is obtained by expanding (1+x+x^3)^n and take the next-to-central column.
A127905
Construct triangle in which n-th row is obtained by expanding (1+x+x^3)^n and take the next-to-central column.
Terms
- a(0) =0a(1) =1a(2) =2a(3) =3a(4) =8a(5) =25a(6) =66a(7) =168a(8) =456a(9) =1269a(10) =3490a(11) =9581a(12) =26544a(13) =73944a(14) =206220a(15) =576045a(16) =1613264a(17) =4527661a(18) =12725946a(19) =35818135a(20) =100950440a(21) =284869263a(22) =804726934a(23) =2275500998a(24) =6440230392a(25) =18242735800a(26) =51714552656
External references
- oeis: A127905