A050100 a(n) = floor(a(n-1)/3) if this is positive and not yet in the sequence, otherwise a(n) = 10*a(n-1).

1, 10, 3, 30, 300, 100, 33, 11, 110, 36, 12, 4, 40, 13, 130, 43, 14, 140, 46, 15, 5, 50, 16, 160, 53, 17, 170, 56, 18, 6, 2, 20, 200, 66, 22, 7, 70, 23, 230, 76, 25, 8, 80, 26, 260, 86, 28, 9, 90, 900, 9000, 3000, 1000, 333, 111, 37, 370

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]], 3]], r, 10 #[[-1]]]] &, {0, 1}, 56] (* Ivan Neretin, Jul 31 2016 *)

PARI

first(n)=my(v=vector(n), t); v[1]=1; for(i=2, n, t=v[i-1]\3; if(t<2, v[i]=10*v[i-1]; next); for(j=1, i-1, if(v[j]==t, v[i]=10*v[i-1]; next(2))); v[i]=t); v \\ Charles R Greathouse IV, Jul 31 2016