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 A050990 #59 Feb 16 2025 08:32:41 %S A050990 4,6,8,10,12,14,22,24,26,30,34,38,46,56,58,62,74,82,86,94,106,118,122, %T A050990 132,134,142,146,158,166,178,182,194,202,206,214,218,226,254,262,274, %U A050990 278,298,302,314,326,334,346,358,362,382,386,394,398,422,446,454,458 %N A050990 2-Knödel numbers. %C A050990 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 A050990 Problem: are there infinitely many 2-Knodel numbers divisible by 4? - _Thomas Ordowski_, Jun 21 2017 %C A050990 Named after the Austrian mathematician and computer scientist Walter Knödel (1926-2018). - _Amiram Eldar_, Jun 08 2021 %H A050990 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 A050990 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 A050990 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/KnoedelNumbers.html">Knödel Numbers</a>. %H A050990 Wikipedia, <a href="https://en.wikipedia.org/wiki/Kn%C3%B6del_number">Knödel number</a>. %t A050990 Select[Range[4, 460, 2], Divisible[# - 2, CarmichaelLambda@ #] &] (* _Michael De Vlieger_, Apr 24 2017 *) %o A050990 (PARI) a002322(n) = lcm(znstar(n)[2]); %o A050990 forstep(n=4, 500, 2, if((n - 2)%a002322(n)==0, print1(n,", "))) \\ _Indranil Ghosh_, Jun 22 2017 %Y A050990 Cf. A002997, A033553, A050992, A050993, A208154, A208155, A208156, A208157, A208158. %K A050990 nonn %O A050990 1,1 %A A050990 _Eric W. Weisstein_