OFFSET
1,2
COMMENTS
This sequence is similar to A355482 except that here all divisors of a(n-1) are counted.
The fixed points in the first 41 terms are 1,2,3,10.
It is unknown if all numbers eventually appear.
Since a(41) has 6144 divisors, a(42) = 2^6144 - 1 is a 1850-digit number.
EXAMPLE
a(7) = 23 = 10111_2 as a(6) = 15 which has four divisors, and 23 is the smallest unused number that has four 1-bits in its binary expansion.
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Scott R. Shannon, Jul 03 2022
STATUS
approved