OFFSET
1,1
COMMENTS
Analogous to A053047 (the same with a similar large initial value, n!).
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..500
FORMULA
a(n) = 2^A053099(n). - Amiram Eldar, Nov 19 2024
EXAMPLE
For n = 6, A002110(6) = 30030, the corresponding iteration chain is {30030, 5760, 1536, 512, 256, 128, 64, 32, 16, 8, 4, 2, 1}. The first power of 2 is the 4th item after 3 iterations. It is 512, therefore a(6) = 512.
MATHEMATICA
a[n_] := 2^ Max@ IntegerExponent[ FixedPointList[ EulerPhi, Times @@ Prime[Range[n]]], 2]; Array[a, 20] (* Giovanni Resta, May 30 2018 *)
PROG
(PARI) a(n) = {my(p = prod(i=1, n, prime(i))); while(p >> valuation(p, 2) > 1, p = eulerphi(p)); 1 << valuation(p, 2); } \\ Amiram Eldar, Nov 19 2024
CROSSREFS
KEYWORD
nonn,changed
AUTHOR
Labos Elemer, Feb 28 2000
EXTENSIONS
a(21)-a(23) from Amiram Eldar, Nov 19 2024
STATUS
approved