Position of n-th 7 in A031111.

Terms

a(0) =11a(1) =18a(2) =21a(3) =26a(4) =28a(5) =63a(6) =65a(7) =103a(8) =109a(9) =125a(10) =127a(11) =147a(12) =165a(13) =176a(14) =187a(15) =215a(16) =218a(17) =244a(18) =248a(19) =249a(20) =251a(21) =288a(22) =291a(23) =296a(24) =305a(25) =319a(26) =346a(27) =353a(28) =355a(29) =361