Apply (1+Shift)^2 to Bell numbers.

Terms

a(0) =1a(1) =3a(2) =5a(3) =10a(4) =27a(5) =87a(6) =322a(7) =1335a(8) =6097a(9) =30304a(10) =162409a(11) =931667a(12) =5686712a(13) =36750201a(14) =250401793a(15) =1792401626a(16) =13436958559a(17) =105208112643a(18) =858286687914