A050136 a(n) = floor(a(n-1)/2) if this is not among 0,a(1),...,a(n-1), otherwise a(n)=5*n.

1, 10, 5, 2, 25, 12, 6, 3, 45, 22, 11, 60, 30, 15, 7, 80, 40, 20, 95, 47, 23, 110, 55, 27, 13, 130, 65, 32, 16, 8, 4, 160, 165, 82, 41, 180, 90, 190, 195, 97, 48, 24, 215, 107, 53, 26, 235, 117, 58, 29, 14, 260, 265, 132, 66, 33, 285, 142, 71, 35, 17, 310, 155, 77, 38, 19, 9, 340, 170, 85, 42, 21

Offset: 1

Author

Clark Kimberling

Keywords

• nonn
• look

Comments

Does this sequence contain every positive integer exactly once?

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A050000, A050128, A050132, A050135.

Programs

Maple

S:= {0,1}: A[1]:= 1:
for n from 2 to 100 do
  v:= floor(A[n-1]/2);
  if not member(v,S) then A[n]:= v
  else A[n]:= 5*n
  fi;
  S:= S union {A[n]};
od:
seq(A[i],i=1..100); # Robert Israel, Aug 07 2018

Mathematica

f[s_List] := Block[{len = Length@s, m = Floor[s[[-1]]/2]}, Append[s, If[MemberQ[s, m], 5 len, m]]]; Rest@ Nest[f, {0, 1}, 65] (* Robert G. Wilson v, Aug 07 2018 *)

Extensions

Corrected by Robert Israel, Aug 07 2018