Generalized Euler numbers O_n^+(2).

Terms

a(0) =1a(1) =2a(2) =5a(3) =16a(4) =61a(5) =275a(6) =1430a(7) =8506a(8) =57205a(9) =432113a(10) =3641288a(11) =34064872a(12) =352200229a(13) =4010179157a(14) =50124636035a(15) =685996839568