A201208 One 1, two 2's, three 1's, four 2's, five 1's, ...

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

Offset

1,2

Links

Table of n, a(n) for n=1..105.

Formula

a(n) = A057212(n) + 1. - T. D. Noe, Nov 28 2011

Example

May be written as a triangle:
  1
  2 2
  1 1 1
  2 2 2 2
  1 1 1 1 1
  2 2 2 2 2 2
  1 1 1 1 1 1 1
Row sums are A022998(n+1).

Mathematica

ReplaceAll[ColumnForm[Table[Mod[k, 2], {k, 12}, {n, k}], Center], 0 -> 2] (* Alonso del Arte, Nov 28 2011 *)

Prog

(Haskell)
a201208 n = a201208_list !! (n-1)
a201208_list = concat $ zipWith ($) (map replicate [1..]) a000034_list
-- Reinhard Zumkeller, Dec 02 2011

Crossrefs

Cf. A057212, A022998.

Cf. A000034.

Sequence in context: A228825 A324381 A331383 * A006513 A105224 A261627

Adjacent sequences: A201205 A201206 A201207 * A201209 A201210 A201211

Keyword

nonn,tabl,easy

Author

Paul Curtz, Nov 28 2011

Extensions

Edited by N. J. A. Sloane, Dec 02 2011

Status

approved