This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A365741 #11 Sep 20 2023 12:21:18 %S A365741 1,5,31,189,1261,9595,77681,654249,5650472 %N A365741 a(n) = A365740(10^n). %C A365741 Pollack et al. listed a(4)-a(6). %H A365741 Paul Pollack, Carl Pomerance and Enrique Treviño, <a href="https://math.dartmouth.edu/~carlp/MonotonePhi.pdf">Sets of monotonicity for Euler's totient function</a>, preprint. See M2(n). %H A365741 Paul Pollack, Carl Pomerance and Enrique Treviño, <a href="https://doi.org/10.1007/s11139-012-9386-6">Sets of monotonicity for Euler's totient function</a>, Ramanujan J. 30 (2013), no. 3, 379--398. %H A365741 Terence Tao, <a href="https://arxiv.org/abs/2309.02325">Monotone non-decreasing sequences of the Euler totient function</a>, arXiv:2309.02325 [math.NT], 2023. %o A365741 (Python) %o A365741 from bisect import bisect %o A365741 from sympy import totient %o A365741 def A365741(n): %o A365741 k = 10**n %o A365741 plist = tuple(totient(i) for i in range(1,k+1) if not isprime(i)) %o A365741 m = len(plist) %o A365741 qlist, c = [0]*(m+1), 0 %o A365741 for i in range(m): %o A365741 qlist[a:=bisect(qlist,plist[i],lo=1,hi=c+1,key=lambda x:plist[x])]=i %o A365741 c = max(c,a) %o A365741 return c %Y A365741 Cf. A000010, A000720. %Y A365741 Cf. A365398, A365399, A365400, A365474, A365737, A365740, A365742, A061070. %K A365741 nonn,hard,more %O A365741 0,2 %A A365741 _Chai Wah Wu_, Sep 17 2023