A111650 2n appears n times (n>0).

2, 4, 4, 6, 6, 6, 8, 8, 8, 8, 10, 10, 10, 10, 10, 12, 12, 12, 12, 12, 12, 14, 14, 14, 14, 14, 14, 14, 16, 16, 16, 16, 16, 16, 16, 16, 18, 18, 18, 18, 18, 18, 18, 18, 18, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 24, 24, 24, 24, 24, 24, 24

Offset: 1

Author

Jonathan Vos Post, Aug 12 2005

Keywords

• easy
• nonn
• tabl

Comments

Seen as a triangle read by rows: T(n,k) = 2*n, 1<=k<=n. - Reinhard Zumkeller, Mar 18 2011

Links

• Reinhard Zumkeller, Rows n = 1..128 of triangle, flattened

Crossrefs

Cf. A000194, A111651, A111652.

Cf. A001650, A193832, A002024.

Programs

Haskell

a111650 n k = a111650_tabl !! (n-1) !! (k-1)
a111650_row n = a111650_tabl !! (n-1)
a111650_tabl = iterate (\xs@(x:_) -> map (+ 2) (x:xs)) [2]
a111650_list = concat a111650_tabl
-- Reinhard Zumkeller, Nov 14 2015, Mar 18 2011

Mathematica

Table[Table[2n,n],{n,12}]//Flatten (* Harvey P. Dale, Apr 21 2018 *)

Python

from math import isqrt
def A111650(n): return isqrt(n<<3)+1&-2 # Chai Wah Wu, Jun 06 2025

Formula

a(n) = 2*A002024(n). - Chai Wah Wu, Jun 06 2025