Numbers n with property that n is not a power of 2 and the finite sequence n, f(n), f(f(n)), ...., 1 in the Collatz (or 3x + 1) problem contains exactly one prime. (The earliest "1" is meant.)
A078440
Numbers n with property that n is not a power of 2 and the finite sequence n, f(n), f(f(n)), ...., 1 in the Collatz (or 3x + 1) problem contains exactly one prime. (The earliest "1" is meant.)
Terms
- a(0) =21a(1) =42a(2) =84a(3) =85a(4) =168a(5) =170a(6) =336a(7) =340a(8) =341a(9) =453a(10) =672a(11) =680a(12) =682a(13) =906a(14) =909a(15) =1344a(16) =1360a(17) =1364a(18) =1365a(19) =1812a(20) =1813a(21) =1818a(22) =2688a(23) =2720a(24) =2728a(25) =2730a(26) =3624a(27) =3626a(28) =3636a(29) =5376
External references
- oeis: A078440