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%I #58 Feb 16 2024 01:22:18
%S 4,6,8,10,12,14,22,24,26,30,34,38,46,56,58,62,74,82,86,94,106,118,122,
%T 132,134,142,146,158,166,178,182,194,202,206,214,218,226,254,262,274,
%U 278,298,302,314,326,334,346,358,362,382,386,394,398,422,446,454,458
%N 2-Knödel numbers.
%C Numbers k > 2 such that A002322(k) divides k-2. Contains all doubled primes and all doubled Carmichael numbers. - _Thomas Ordowski_, Apr 23 2017
%C Problem: are there infinitely many 2-Knodel numbers divisible by 4? - _Thomas Ordowski_, Jun 21 2017
%C Named after the Austrian mathematician and computer scientist Walter Knödel (1926-2018). - _Amiram Eldar_, Jun 08 2021
%H Amiram Eldar, <a href="/A050990/b050990.txt">Table of n, a(n) for n = 1..10000</a> (first 690 terms from R. J. Mathar)
%H John H. Castillo and Jhony Fernando Caranguay Mainguez, <a href="https://arxiv.org/abs/1708.06812">The set of k-units modulo n</a>, arXiv:1708.06812 [math.NT], 2017.
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/KnoedelNumbers.html">Knödel Numbers</a>.
%H Wikipedia, <a href="https://en.wikipedia.org/wiki/Kn%C3%B6del_number">Knödel number</a>.
%t Select[Range[4, 460, 2], Divisible[# - 2, CarmichaelLambda@ #] &] (* _Michael De Vlieger_, Apr 24 2017 *)
%o (PARI) a002322(n) = lcm(znstar(n)[2]);
%o forstep(n=4, 500, 2, if((n - 2)%a002322(n)==0, print1(n,", "))) \\ _Indranil Ghosh_, Jun 22 2017
%Y Cf. A002997, A033553, A050992, A050993, A208154, A208155, A208156, A208157, A208158.
%K nonn
%O 1,1
%A _Eric W. Weisstein_
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