G.f.: 1/(1-7*x+35*x^3-35*x^4+7*x^6-x^7).

Terms

a(0) =1a(1) =7a(2) =49a(3) =308a(4) =1946a(5) =12152a(6) =75992a(7) =474566a(8) =2964416a(9) =18514405a(10) =115637431a(11) =722234149a(12) =4510869636a(13) =28173535572a(14) =175963587528