A333913 Numbers k such that lambda(k) is not the sum of 3 squares, where lambda is the Carmichael lambda function (A002322).

29, 58, 61, 87, 113, 116, 122, 143, 145, 155, 157, 169, 174, 175, 183, 225, 226, 232, 235, 241, 244, 286, 290, 305, 310, 314, 317, 325, 338, 339, 348, 349, 350, 366, 371, 385, 395, 403, 427, 429, 435, 449, 450, 452, 464, 465, 470, 471, 477, 482, 488, 493, 495

Offset: 1

Author

Amiram Eldar, Apr 09 2020

Keywords

• nonn

Comments

Pollack (2011) proved that this sequence has a lower and an upper asymptotic densities, and conjectured that they do not coincide.

Examples

			1 is not a term since lambda(1) = 1 = 0^2 + 0^2 + 1^2 is the sum of 3 squares.
29 is a term since lambda(29) = 28 is not the sum of 3 squares.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000
• Paul Pollack, Values of the Euler and Carmichael functions which are sums of three squares, Integers, Vol. 11 (2011), pp. 145-161.

Crossrefs

Cf. A002322, A004215, A173694, A272405, A333912.

Programs

Mathematica

Select[Range[500], SquaresR[3, CarmichaelLambda[#]] == 0 &]