a(n) = Sum_{k=0..floor(n/6)} (-1)^k * (7*k+1) * binomial(2*n-5*k+1,n-6*k)/(2*n-5*k+1).

A390477

a(n) = Sum_{k=0..floor(n/6)} (-1)^k * (7*k+1) * binomial(2*n-5*k+1,n-6*k)/(2*n-5*k+1).

Terms

    a(0) =1a(1) =1a(2) =2a(3) =5a(4) =14a(5) =42a(6) =131a(7) =421a(8) =1386a(9) =4654a(10) =15886a(11) =54978a(12) =192509a(13) =680899a(14) =2429418a(15) =8734395a(16) =31613985a(17) =115109388a(18) =421354939a(19) =1549721348a(20) =5724315670a(21) =21226681986a(22) =78990800097a(23) =294899059900

External references