Position of n-th 4 in A030998.

Terms

a(0) =4a(1) =16a(2) =30a(3) =44a(4) =49a(5) =51a(6) =53a(7) =55a(8) =57a(9) =58a(10) =59a(11) =61a(12) =72a(13) =86a(14) =105a(15) =126a(16) =147a(17) =168a(18) =176a(19) =179a(20) =182a(21) =185a(22) =188a(23) =189a(24) =191a(25) =194a(26) =210a(27) =231a(28) =252a(29) =273