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