Position of n-th 4 in A031100.

Terms

a(0) =10a(1) =28a(2) =33a(3) =35a(4) =37a(5) =39a(6) =46a(7) =64a(8) =85a(9) =112a(10) =132a(11) =135a(12) =138a(13) =139a(14) =141a(15) =144a(16) =166a(17) =193a(18) =220a(19) =247a(20) =255a(21) =258a(22) =261a(23) =264a(24) =274a(25) =301a(26) =328a(27) =355a(28) =375a(29) =378