Position of n-th 4 in A031235.

Terms

a(0) =4a(1) =13a(2) =23a(3) =33a(4) =36a(5) =38a(6) =40a(7) =42a(8) =43a(9) =44a(10) =57a(11) =72a(12) =87a(13) =102a(14) =106a(15) =109a(16) =112a(17) =115a(18) =117a(19) =118a(20) =132a(21) =147a(22) =162a(23) =177a(24) =181a(25) =184a(26) =187a(27) =190a(28) =192a(29) =193