First occurrence of 2*n in A035096.

Terms

a(0) =2a(1) =4a(2) =7a(3) =20a(4) =8a(5) =17a(6) =39a(7) =134a(8) =45a(9) =206a(10) =149a(11) =49a(12) =66a(13) =321a(14) =88a(15) =98a(16) =637a(17) =382a(18) =259a(19) =284a(20) =820a(21) =302a(22) =310a(23) =1102a(24) =1597a(25) =3763a(26) =1140a(27) =3432a(28) =741a(29) =532