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

Author

Paul Curtz, Nov 28 2011

Keywords

• nonn
• tabl
• easy

Examples

			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).
		

Crossrefs

Cf. A057212, A022998.

Cf. A000034.

Programs

Haskell

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

Mathematica

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

Formula

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

Extensions

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