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 A283656 #48 Aug 26 2019 05:48:39 %S A283656 65,91,217,273,451,481,703,793,1281,1729,1891,1921,2465,2701,3201, %T A283656 4033,4097,4681,5833,6643,6697,7105,7161,8321,8401,8911,9073,10649, %U A283656 11041,11476,11521,12403,12545,13051,14689,14701,15841,16385,16401,16471,18361,18705,18721,19684,19951,20801,21953,22177,22681,23001 %N A283656 Numbers n such that gcd(phi(n), n-1) > lambda(n). %C A283656 All terms are composite. No powers of primes. %C A283656 Contains all Carmichael numbers except A264012. %C A283656 If n is in the sequence, then n-1 is not squarefree. %C A283656 Problem: are there infinitely many such even numbers? : 11476, 19684, 24564, 37576, 57226, 65026, 80476, 89776, 91356, ... %C A283656 It is possible to show there are infinitely many Carmichael numbers with the property. In fact this follows with a small modification of the original proof of the infinitude of the Carmichael numbers. It seems harder though to prove that there are infinitely many non-Carmichaels with the property, though undoubtedly it's true. - Carl Pomerance, Mar 24 2017 %H A283656 Amiram Eldar, <a href="/A283656/b283656.txt">Table of n, a(n) for n = 1..10000</a> %t A283656 Select[Range[10^4], GCD[EulerPhi[#], #-1] > CarmichaelLambda[#] &] (* _Amiram Eldar_, Aug 26 2019 *) %Y A283656 Cf. A000010, A002322, A002997, A049559, A264012. %K A283656 nonn %O A283656 1,1 %A A283656 _Thomas Ordowski_ and _Altug Alkan_, Mar 23 2017