OFFSET
1,1
COMMENTS
In these iteration chains the number of non-2-powers seem to be dominant.
The sequence is not monotonic.
EXAMPLE
For n=10, the iteration chain of 43 terms is {6469693230, 5447823150, 4315810350, ..., 188416, 98304, 65536, 32768, ..., 4, 2, 1, 0} in which the largest power of 2 is 65536 = 2^16.
For n=11 the length is 61, including 54 numbers that are not powers of 2, and 7 powers of 2, of which the largest is 64 = a(11) < a(10) = 65536.
MATHEMATICA
Table[SelectFirst[NestWhileList[# - EulerPhi@ # &, P, # > 0 &], IntegerQ@ Log2@ # &], {P, FoldList[Times, Prime@ Range@ 30]}] (* Michael De Vlieger, Jun 11 2018 *)
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Labos Elemer, Feb 28 2000
EXTENSIONS
More terms from Michael De Vlieger, Jun 11 2018
a(41)-a(44) from Jinyuan Wang, Jul 12 2021
STATUS
approved