A067017 Start with a(0)=1, a(1)=4, a(2)=3, a(3)=2; for n>=3, a(n+1) = mex_i (a(i)+a(n-i)), where mex means smallest nonnegative missing number.

1, 4, 3, 2, 0, 0, 0, 0, 0, 5, 1, 1, 1, 1, 1, 6, 2, 2, 0, 0, 0, 0, 0, 5, 1, 1, 1, 1, 1, 6, 2, 2, 0, 0, 0, 0, 0, 5, 1, 1, 1, 1, 1, 6, 2, 2, 0, 0, 0, 0, 0, 5, 1, 1, 1, 1, 1, 6, 2, 2, 0, 0, 0, 0, 0, 5, 1, 1, 1, 1, 1, 6, 2, 2, 0, 0, 0, 0, 0, 5, 1, 1, 1, 1, 1, 6, 2, 2, 0, 0, 0, 0, 0, 5, 1, 1, 1, 1, 1, 6, 2, 2, 0, 0, 0

Offset: 0

Author

N. J. A. Sloane, Feb 17 2002

Keywords

• nonn
• easy

References

• R. K. Guy, Unsolved Problems in Number Theory, E27.

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 0..10000

Crossrefs

Cf. A067016, A067018.

Programs

Haskell

import Data.List ((\\))
a067017 n = a067017_list !! n
a067017_list =  [1,4,3,2] ++ f [2,3,4,1] where
  f xs = mexi : f (mexi : xs) where
    mexi = head $ [0..] \\ zipWith (+) xs (reverse xs)
-- Reinhard Zumkeller, May 05 2012

Extensions

More terms from John W. Layman, Feb 20 2002