A050112 a(n) = floor(a(n-1)/4) if this is positive and not yet in the sequence, otherwise a(n) = 6*a(n-1).

1, 6, 36, 9, 2, 12, 3, 18, 4, 24, 144, 864, 216, 54, 13, 78, 19, 114, 28, 7, 42, 10, 60, 15, 90, 22, 5, 30, 180, 45, 11, 66, 16, 96, 576, 3456, 20736, 5184, 1296, 324, 81, 20, 120, 720, 4320, 1080, 270, 67, 402, 100, 25, 150, 37, 222, 55

Offset: 1

Author

Clark Kimberling

Keywords

• nonn

Links

• Ivan Neretin, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A050000 and references therein.

Programs

Mathematica

Rest@Nest[Append[#, If[FreeQ[#, r = Quotient[#[[-1]], 4]], r, 6 #[[-1]]]] &, {0, 1}, 54] (* Ivan Neretin, Jul 31 2016 *)

PARI

first(n)=my(v=vector(n),t); v[1]=1; for(i=2,n, t=v[i-1]\4; if(t<2, v[i]=6*v[i-1]; next); for(j=1,i-1, if(v[j]==t, v[i]=6*v[i-1]; next(2))); v[i]=t); v \\ Charles R Greathouse IV, Jul 31 2016