Position of n-th 4 in A030548.

Terms

a(0) =4a(1) =15a(2) =27a(3) =39a(4) =42a(5) =44a(6) =46a(7) =48a(8) =50a(9) =51a(10) =52a(11) =63a(12) =80a(13) =98a(14) =116a(15) =134a(16) =139a(17) =142a(18) =145a(19) =148a(20) =151a(21) =152a(22) =154a(23) =170a(24) =188a(25) =206a(26) =224a(27) =242a(28) =247a(29) =250