OFFSET
1,2
COMMENTS
This sequence is a self-inverse permutation of the natural numbers.
A priori, there are only two fixed points: 1 and 2 (note that a fixed point must be a power of 2).
This sequence is related to A266195: here n * a(n), there a(n) * a(n+1), does not produce any carries when performed in base 2.
LINKS
EXAMPLE
1 * 1 can be computed without carry in base 2, hence a(1) = 1.
2 * 2 can be computed without carry in base 2, hence a(2) = 2.
3 * 3 cannot be computed without carry in base 2.
3 * 4 can be computed without carry in base 2, hence a(3) = 4.
PROG
(PARI) See Links section.
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Rémy Sigrist, Jul 10 2017
STATUS
approved