Number of relations on an infinite set.

Terms

a(0) =1a(1) =2a(2) =9a(3) =37a(4) =183a(5) =933a(6) =5314a(7) =32043a(8) =207212a(9) =1415934a(10) =10200289a(11) =77018442a(12) =607474564a(13) =4987909231a(14) =42519634303a(15) =375395726926