A125217 Numbers that can be written uniquely as 4*x*y-x-y with 1<=x<=y.

2, 5, 8, 11, 12, 14, 17, 19, 20, 23, 29, 30, 32, 33, 35, 38, 40, 44, 50, 52, 53, 54, 59, 61, 62, 63, 65, 75, 77, 80, 82, 83, 85, 90, 92, 95, 98, 103, 104, 109, 113, 117, 118, 119, 122, 124, 125, 129, 132, 134, 137, 138, 143, 145, 147, 149, 151, 158, 159, 162, 164, 167

Offset: 1

Author

Reinhard Zumkeller, Nov 24 2006

Keywords

• nonn

Comments

A125203(a(n)) = 1.

A124934 is the union of this sequence and A125218.

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Programs

Haskell

import Data.List (elemIndices)
a125217 n = a125217_list !! (n-1)
a125217_list = map (+ 1) $ elemIndices 1 a125203_list
-- Reinhard Zumkeller, Jan 02 2013