A099257 a(1)=1, a(n+1) = if a(n)=n then 2*n+1 else smallest number not occurring earlier.

1, 3, 2, 4, 9, 5, 6, 7, 8, 10, 21, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 22, 45, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 46, 93, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71

Offset: 1

Author

Reinhard Zumkeller, Oct 09 2004

Keywords

• nonn

Comments

Permutation of the natural numbers with inverse A099258;

a(A033484(n)) = A033484(n);

a(A033484(n) + 1) = 2*A033484(n) + 1 = A068156(n).

Links

• Index entries for sequences that are permutations of the natural numbers

Formula

a(n) = if n = 3*2^k - 2 then n else (if n = 3*2^k - 1 then 2*n + 1 else n - 1).