A050012 a(n) = floor(a(n-1)/2) if this is positive and not yet in the sequence, otherwise a(n) = 7*a(n-1).

1, 7, 3, 21, 10, 5, 2, 14, 98, 49, 24, 12, 6, 42, 294, 147, 73, 36, 18, 9, 4, 28, 196, 1372, 686, 343, 171, 85, 595, 297, 148, 74, 37, 259, 129, 64, 32, 16, 8, 56, 392, 2744, 19208, 9604, 4802, 2401, 1200, 600, 300, 150, 75, 525, 262

Offset: 1

Author

Clark Kimberling

Keywords

• nonn
• easy

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]], 2]], r, 7 #[[-1]]]] &, {0, 1}, 52] (* Ivan Neretin, Jul 31 2016 *)

PARI

first(n)=my(v=vector(n),t); v[1]=1; for(i=2,n, t=v[i-1]\2; if(t<2, v[i]=7*v[i-1]; next); for(j=1,i-1, if(v[j]==t, v[i]=7*v[i-1]; next(2))); v[i]=t); v \\ Charles R Greathouse IV, Jul 31 2016