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 A286265 #19 Jul 17 2021 23:31:35 %S A286265 5,7,11,13,17,19,23,25,29,31,33,35,37,41,43,47,49,51,53,55,59,61,65, %T A286265 67,69,71,73,77,79,83,85,87,89,91,95,97,101,103,107,109,113,115,119, %U A286265 121,123,125,127,131,133,137,139,141,143,145,149,151,153,155,157 %N A286265 Totient abundant numbers: numbers k such that A092693(k) > k. %H A286265 Amiram Eldar, <a href="/A286265/b286265.txt">Table of n, a(n) for n = 1..10000</a> %H A286265 Paul Loomis and Florian Luca, <a href="https://www.emis.de/journals/INTEGERS/papers/i6/i6.Abstract.html">On totient abundant numbers</a>, Electronic Journal of Combinatorial Number Theory, Vol. 8, #A06 (2008). %e A286265 19 is a totient abundant number since A092693(19) = phi(19) + phi(phi(19)) + ... = 18 + 6 + 2 + 1 = 27 > 19. %t A286265 totAbundantQ[n_] := Plus @@ FixedPointList[ EulerPhi@ # &, n] > 2*n+1; Select[Range[1000],totAbundantQ] %o A286265 (Python) %o A286265 from sympy import totient %o A286265 def a092693(n): return 0 if n==1 else totient(n) + a092693(totient(n)) %o A286265 print([n for n in range(1, 201) if a092693(n) > n]) # _Indranil Ghosh_, May 05 2017 %Y A286265 Cf. A000010, A082897, A092693. %K A286265 nonn %O A286265 1,1 %A A286265 _Amiram Eldar_, May 05 2017