Denominators of Bernoulli numbers interleaved with even numbers.

Terms

a(0) =1a(1) =2a(2) =6a(3) =4a(4) =30a(5) =6a(6) =42a(7) =8a(8) =30a(9) =10a(10) =66a(11) =12a(12) =2730a(13) =14a(14) =6a(15) =16a(16) =510a(17) =18a(18) =798a(19) =20a(20) =330a(21) =22a(22) =138a(23) =24a(24) =2730a(25) =26a(26) =6a(27) =28a(28) =870a(29) =30