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A064238 Values of m such that N = (am+1)(bm+1)(cm+1) is a 3-Carmichael number (A087788), where a,b,c = 1,2,3.

%I A064238 #29 Jun 25 2023 18:06:48
%S A064238 6,36,210,270,306,330,336,600,726,1170,1236,1296,1530,1656,2220,2280,
%T A064238 2556,3036,3060,3066,4260,4446,4800,4950,5226,5580,5850,6150,6360,
%U A064238 6690,6840,6966,7620,7680,7686,7866,8016,8166,8190,8286,8520,8526,8646,8940,9090
%N A064238 Values of m such that N = (am+1)(bm+1)(cm+1) is a 3-Carmichael number (A087788), where a,b,c = 1,2,3.
%C A064238 am+1, bm+1, cm+1 are primes and am | (N-1), bm | (N-1), cm |(N-1).
%C A064238 All m's are multiples of 6 and m, 2m and 3m divide m(2m+1)(3m+1)-1 automatically.
%D A064238 Harvey Dubner (harvey(AT)dubner.com), personal communication, Jun 27 2001.
%H A064238 Amiram Eldar, <a href="/A064238/b064238.txt">Table of n, a(n) for n = 1..10000</a>
%F A064238 a(n) = 6 * A046025(n).
%p A064238 q:= n-> andmap(isprime, [6*j*n+1$j=1..3]):
%p A064238 map(x-> 6*x, select(q, [$1..2000]))[];  # _Alois P. Heinz_, Jun 25 2023
%t A064238 CarmichaelNbrQ[n_] := ! PrimeQ@ n && Mod[n, CarmichaelLambda[n]] == 1; Select[ Range@ 9000, PrimeQ[# + 1] && PrimeQ[2# + 1] && PrimeQ[3# + 1] && CarmichaelNbrQ[(# + 1)(2 # + 1)(3 # + 1)] &] (* _Robert G. Wilson v_, Aug 23 2012 *)
%Y A064238 Cf. A046025, A087788.
%K A064238 nonn
%O A064238 1,1
%A A064238 _N. J. A. Sloane_, Sep 23 2001
%E A064238 Offset corrected by _Amiram Eldar_, Oct 16 2019