a(n) is the number of integers m which take n steps to reach 1 in '3x+1' problem.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =2a(6) =2a(7) =4a(8) =4a(9) =6a(10) =6a(11) =8a(12) =10a(13) =14a(14) =18a(15) =24a(16) =29a(17) =36a(18) =44a(19) =58a(20) =72a(21) =91a(22) =113a(23) =143a(24) =179a(25) =227a(26) =287a(27) =366a(28) =460a(29) =578