a(n) = (1 + number of halving and tripling steps to reach 1 in the Collatz (3x+1) problem), or -1 if 1 is never reached.

A008908

a(n) = (1 + number of halving and tripling steps to reach 1 in the Collatz (3x+1) problem), or -1 if 1 is never reached.

Terms

    a(0) =1a(1) =2a(2) =8a(3) =3a(4) =6a(5) =9a(6) =17a(7) =4a(8) =20a(9) =7a(10) =15a(11) =10a(12) =10a(13) =18a(14) =18a(15) =5a(16) =13a(17) =21a(18) =21a(19) =8a(20) =8a(21) =16a(22) =16a(23) =11a(24) =24a(25) =11a(26) =112a(27) =19a(28) =19a(29) =19

External references