OFFSET
1,2
COMMENTS
Conjecture: there are infinitely many pairs of the form a(x) = y; a(y) = x (see examples).
First differs from A351903 at a(11).
EXAMPLE
For n = 11 we have that 6 is the smallest number k with at least one subpart 11 in the symmetric representation of sigma(k), so a(11) = 6.
The symmetric representation of sigma(6) in the first quadrant looks like this:
.
_ _ _ _
|_ _ _ |_ 1
| |_|_ 11
|_ _ |
| |
| |
|_|
.
There are one subpart 11 and one subpart 1.
.
Some pairs of the form a(x) = y; a(y) = x:
a(2) = 3; a(3) = 2.
a(4) = 7; a(7) = 4.
a(6) = 11; a(11) = 6.
a(8) = 15; a(15) = 8.
a(16) = 31; a(31) = 16.
.
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Omar E. Pol, Feb 25 2022
STATUS
approved