A260822 - OEIS

%I #30 Aug 04 2015 20:44:46

%S 3,4,1,2,7,8,5,6,11,12,9,10,14,13,17,18,15,16,20,19,23,24,21,22,26,25,

%T 28,27,31,32,29,30,35,36,33,34,38,37,41,42,39,40,44,43,46,45,48,47,50,

%U 49,53,54,51,52,56,55,58,57,60,59,62,61,65,66,63,64,68

%N Lexicographically smallest permutation of the natural numbers, such that a(n)+n is a composite number and a(n) != n.

%C The permutation is self-inverse: a(a(n)) = n;

%C by definition there are no fixed points.

%H Reinhard Zumkeller, <a href="/A260822/b260822.txt">Table of n, a(n) for n = 1..10000</a>

%H <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a>

%o (Haskell)

%o import Data.List (delete)

%o a260822 n = a260822_list !! (n-1)

%o a260822_list = f 1 [1..] where

%o    f x zs = g zs where

%o      g (y:ys) = if y /= x && a010051' (x + y) == 0

%o                    then y : f (x + 1) (delete y zs) else g ys

%Y Cf. A010051, A002808, A260933.

%K nonn

%O 1,1

%A _Reinhard Zumkeller_, Aug 04 2015