A binomial convolution.

Terms

a(0) =1a(1) =1a(2) =5a(3) =17a(4) =69a(5) =339a(6) =1677a(7) =9321a(8) =55137a(9) =343659a(10) =2285289a(11) =15910857a(12) =116120781a(13) =886308147a(14) =7033465989a(15) =58008074409a(16) =495792941337