a(n) = position of the first n in A026409.

Terms

a(0) =1a(1) =2a(2) =3a(3) =5a(4) =7a(5) =8a(6) =11a(7) =13a(8) =16a(9) =20a(10) =24a(11) =29a(12) =32a(13) =37a(14) =38a(15) =46a(16) =50a(17) =59a(18) =61a(19) =68a(20) =76a(21) =78a(22) =91a(23) =92a(24) =105a(25) =111a(26) =112a(27) =126a(28) =136a(29) =146