Even terms in A260442 (in A260443).

Terms

a(0) =2a(1) =6a(2) =18a(3) =30a(4) =90a(5) =210a(6) =270a(7) =450a(8) =630a(9) =2310a(10) =6750a(11) =6930a(12) =9450a(13) =15750a(14) =20250a(15) =22050a(16) =30030a(17) =47250a(18) =90090a(19) =330750a(20) =510510a(21) =727650a(22) =1212750a(23) =1531530a(24) =1653750a(25) =2668050a(26) =3543750a(27) =4961250a(28) =8489250a(29) =9699690