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 A050990 2-Knödel numbers. 15
 4, 6, 8, 10, 12, 14, 22, 24, 26, 30, 34, 38, 46, 56, 58, 62, 74, 82, 86, 94, 106, 118, 122, 132, 134, 142, 146, 158, 166, 178, 182, 194, 202, 206, 214, 218, 226, 254, 262, 274, 278, 298, 302, 314, 326, 334, 346, 358, 362, 382, 386, 394, 398, 422, 446, 454, 458 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Numbers k > 2 such that A002322(k) divides k-2. Contains all doubled primes and all doubled Carmichael numbers. - Thomas Ordowski, Apr 23 2017 Problem: are there infinitely many 2-Knodel numbers divisible by 4? - Thomas Ordowski, Jun 21 2017 LINKS Amiram Eldar, Table of n, a(n) for n = 1..10000 (first 690 terms from R. J. Mathar) John H. Castillo and Jhony Fernando Caranguay Mainguez, The set of k-units modulo n, arXiv:1708.06812 [math.NT], 2017. Eric Weisstein's World of Mathematics, Knödel Numbers. MAPLE with(numtheory); knodel:=proc(i, k) local a, n, ok; for n from k+1 to i do   ok:=1;   for a from 1 to n do      if gcd(a, n)=1 then  if (a^(n-k) mod n)<>1 then ok:=0; break; fi; fi;   od;   if ok=1 then print(n); fi; od; end: knodel(1000, 2) # Paolo P. Lava, Feb 24 2012 MATHEMATICA Select[Range[4, 460, 2], Divisible[# - 2, CarmichaelLambda@ #] &] (* Michael De Vlieger, Apr 24 2017 *) PROG (PARI) a002322(n) = lcm(znstar(n)[2]); forstep(n=4, 500, 2, if((n - 2)%a002322(n)==0, print1(n, ", "))) \\ Indranil Ghosh, Jun 22 2017 CROSSREFS Cf. A002997, A033553, A050992, A050993, A208154, A208155, A208156, A208157, A208158. Sequence in context: A061344 A066664 A064938 * A289425 A225514 A161546 Adjacent sequences:  A050987 A050988 A050989 * A050991 A050992 A050993 KEYWORD nonn AUTHOR STATUS approved

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Last modified October 18 08:08 EDT 2019. Contains 328146 sequences. (Running on oeis4.)