[seqfan] Re: Exchange rightmost two base-4 digits of n>1; a(0)=0, a(1)=4. (base 4 analogue of what A181099 is in base 3, and A080412 is base 2

[Georgi Guninski]

On Mon, Oct 11, 2010 at 12:02:31AM -0700, Jonathan Post wrote:
> 
> Exchange rightmost two base-4 digits of n>1; a(0)=0, a(1)=4.
> 
> 0, 4, 8, 12, 1, 5, 9, 13, 2, 6, 10, 14, 3, 7, 11, 15, 16, 20, 24, 28,
> 17, 21, 25, 29, 18, 22, 26, 30, 19, 23, 27, 31, 32, 36, 40, 44, 33,
> 37, 41, 45, 34, 38, 42, 46, 35, 39, 43, 47, 48, 52, 56, 60, 49, 53,
> 57, 61, 50
>

first differences seem periodic:
[4, 4, 4, -11, 4, 4, 4, -11, 4, 4, 4, 1, 4, 4, 4, -11, ...]