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 A333913 #10 Apr 12 2020 09:50:02 %S A333913 29,58,61,87,113,116,122,143,145,155,157,169,174,175,183,225,226,232, %T A333913 235,241,244,286,290,305,310,314,317,325,338,339,348,349,350,366,371, %U A333913 385,395,403,427,429,435,449,450,452,464,465,470,471,477,482,488,493,495 %N A333913 Numbers k such that lambda(k) is not the sum of 3 squares, where lambda is the Carmichael lambda function (A002322). %C A333913 Pollack (2011) proved that this sequence has a lower and an upper asymptotic densities, and conjectured that they do not coincide. %H A333913 Amiram Eldar, <a href="/A333913/b333913.txt">Table of n, a(n) for n = 1..10000</a> %H A333913 Paul Pollack, <a href="https://www.emis.de/journals/INTEGERS/papers/l13/l13.Abstract.html">Values of the Euler and Carmichael functions which are sums of three squares</a>, Integers, Vol. 11 (2011), pp. 145-161. %e A333913 1 is not a term since lambda(1) = 1 = 0^2 + 0^2 + 1^2 is the sum of 3 squares. %e A333913 29 is a term since lambda(29) = 28 is not the sum of 3 squares. %t A333913 Select[Range[500], SquaresR[3, CarmichaelLambda[#]] == 0 &] %Y A333913 Cf. A002322, A004215, A173694, A272405, A333912. %K A333913 nonn %O A333913 1,1 %A A333913 _Amiram Eldar_, Apr 09 2020