a(n) = hypergeom([-2*n-1, 1/2], [2], 4) + (2*n+1)*hypergeom([-n+1/2, -n], [2], 4).

A273019

a(n) = hypergeom([-2*n-1, 1/2], [2], 4) + (2*n+1)*hypergeom([-n+1/2, -n], [2], 4).

Terms

    a(0) =1a(1) =5a(2) =39a(3) =321a(4) =2675a(5) =22483a(6) =190345a(7) =1621413a(8) =13882947a(9) =119385663a(10) =1030434069a(11) =8921880135a(12) =77459553549a(13) =674100041501

External references