a(2n) = numerator of |Bernoulli(2n)|, a(2n+1) = Euler(2n).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =5a(6) =1a(7) =61a(8) =1a(9) =1385a(10) =5a(11) =50521a(12) =691a(13) =2702765a(14) =7a(15) =199360981a(16) =3617a(17) =19391512145a(18) =43867a(20) =174611a(22) =854513a(24) =236364091a(26) =8553103a(28) =23749461029