Index of 4^n within the sequence of the numbers of the form 3^i*4^j.

Terms

a(0) =1a(1) =3a(2) =6a(3) =10a(4) =16a(5) =23a(6) =31a(7) =40a(8) =51a(9) =63a(10) =76a(11) =90a(12) =106a(13) =123a(14) =141a(15) =160a(16) =181a(17) =203a(18) =226a(19) =250a(20) =276a(21) =303a(22) =331a(23) =361a(24) =392a(25) =424a(26) =457a(27) =492a(28) =528a(29) =565