A "cosh transform" of binomial(2n,n-1).

Terms

a(0) =0a(1) =1a(2) =4a(3) =18a(4) =80a(5) =365a(6) =1692a(7) =7945a(8) =37648a(9) =179595a(10) =861020a(11) =4143832a(12) =20004096a(13) =96810779a(14) =469508340a(15) =2281123530a(16) =11100465216a(17) =54093131147a(18) =263929559436