Odd Bell numbers.

Terms

a(0) =1a(1) =1a(2) =5a(3) =15a(4) =203a(5) =877a(6) =21147a(7) =115975a(8) =4213597a(9) =27644437a(10) =1382958545a(11) =10480142147a(12) =682076806159