OFFSET
0,2
COMMENTS
Pollack et al. listed a(4)-a(6).
LINKS
Paul Pollack, Carl Pomerance and Enrique Treviño, Sets of monotonicity for Euler's totient function, preprint. See M2(n).
Paul Pollack, Carl Pomerance and Enrique Treviño, Sets of monotonicity for Euler's totient function, Ramanujan J. 30 (2013), no. 3, 379--398.
Terence Tao, Monotone non-decreasing sequences of the Euler totient function, arXiv:2309.02325 [math.NT], 2023.
PROG
(Python)
from bisect import bisect
from sympy import totient
def A365741(n):
k = 10**n
plist = tuple(totient(i) for i in range(1, k+1) if not isprime(i))
m = len(plist)
qlist, c = [0]*(m+1), 0
for i in range(m):
qlist[a:=bisect(qlist, plist[i], lo=1, hi=c+1, key=lambda x:plist[x])]=i
c = max(c, a)
return c
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Chai Wah Wu, Sep 17 2023
STATUS
approved