a(n) = Sum_{k=0..n} binomial(n, ceiling(k/2)) * binomial(n, floor(k/2)).

A360861

a(n) = Sum_{k=0..n} binomial(n, ceiling(k/2)) * binomial(n, floor(k/2)).

Terms

    a(0) =1a(1) =2a(2) =7a(3) =22a(4) =81a(5) =281a(6) =1058a(7) =3830a(8) =14605a(9) =54127a(10) =208110a(11) =782761a(12) =3027038a(13) =11501478a(14) =44668692a(15) =170974710a(16) =666220005a(17) =2564271875a(18) =10018268150a(19) =38728479647a(20) =151631858378a(21) =588229029258

External references