Second-order Euler numbers.

Terms

a(0) =0a(1) =2a(2) =6a(3) =28a(4) =180a(5) =662a(6) =7266a(7) =24568a(8) =408360a(9) =1326122a(10) =30974526a(11) =98329108a(12) =3065784540a(13) =9596075582a(14) =384653685786