A346707 "Look once to the left" sequence, omitting a(k) for each iteration k, starting with 1,2 (see example).

1, 2, 2, 1, 2, 1, 2, 1, 2, 1, 2, 2, 2, 1, 2, 1, 2, 1, 2, 2, 1, 1, 2, 1, 2, 1, 2, 2, 2, 1, 2, 1, 2, 1, 2, 2, 1, 2, 2, 1, 2, 1, 2, 2, 2, 1, 2, 1, 2, 1, 2, 2, 1, 1, 2, 1, 2, 1, 2, 2, 2, 1, 2, 1, 2, 1, 2, 2, 1, 2, 1, 1, 2, 1, 2, 2, 2, 1, 2, 1, 2, 1, 2, 2, 1, 1, 2

Offset: 1

Author

Matthew Malone, Jul 29 2021

Keywords

• nonn

Comments

The ratio of number of 2's to number of 1's appears to converge to 1.3985918...

Examples

			Begin with [1, 2].
Iteration 1: append to self, omitting term 1: [1, 2] + [2] = [1, 2, 2].
Iteration 2: append to self, omitting term 2: [1, 2, 2] + [1, 2] = [1, 2, 2, 1, 2].
Iteration 3: append to self, omitting term 3: [1, 2, 2, 1, 2] + [1, 2, 1, 2] = [1, 2, 2, 1, 2, 1, 2, 1, 2].
		

Crossrefs

Cf. A000051, A293838.

Programs

Mathematica

Block[{a = {1, 2}}, Do[a = Join[a, Delete[a, i]], {i, 7}]; a] (* Michael De Vlieger, Aug 04 2021 *)

PARI

a(n) = n-=2; while(n>0, my(k=logint(n,2)); n-=1<Kevin Ryde, Aug 03 2021

Python

def sequence(iterations, start=[1,2]):
  a = start
  for k in range(0, iterations):
    a = a + a[:k] + a[k+1:]
  return a