a(n) = Sum_{k=0..n} binomial(n, floor(k/2 - 1/2)) * binomial(n, ceiling(k/2 - 1/2)).

A378069

a(n) = Sum_{k=0..n} binomial(n, floor(k/2 - 1/2)) * binomial(n, ceiling(k/2 - 1/2)).

Terms

    a(0) =0a(1) =1a(2) =3a(3) =13a(4) =45a(5) =181a(6) =658a(7) =2605a(8) =9705a(9) =38251a(10) =144606a(11) =569317a(12) =2173262a(13) =8556822a(14) =32890068a(15) =129565485a(16) =500583105a(17) =1973295775a(18) =7654363750a(19) =30194784763a(20) =117497078842a(21) =463820452602

External references