A064240 Values of m such that N=(am+1)(bm+1)(cm+1) is a 3-Carmichael number (A087788), where a,b,c = 1,2,7.

30, 156, 618, 660, 1626, 2550, 4230, 4356, 4566, 5658, 6120, 6708, 7506, 11496, 15318, 16746, 18048, 19140, 19476, 19686, 20610, 21030, 22920, 23130, 24096, 25188, 26406, 27918, 29346, 29598, 29640, 32748, 33966, 35058, 39678, 41610

Offset: 1

Author

N. J. A. Sloane, Sep 23 2001

Keywords

• nonn

Comments

am+1, bm+1, cm+1 are primes and am | (N-1), bm | (N-1), cm |(N-1).

References

• Harvey Dubner (harvey(AT)dubner.com), personal communication, Jun 27 2001.

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A087788.

Programs

Mathematica

CarmichaelNbrQ[n_] := ! PrimeQ@ n && Mod[n, CarmichaelLambda@ n] == 1; Select[ Range@ 42000, PrimeQ[# + 1] && PrimeQ[2# + 1] && PrimeQ[7# + 1] && CarmichaelNbrQ[(# + 1)(2# + 1)(7# + 1)] &] (* Robert G. Wilson v, Aug 23 2012 *)

Extensions

Offset corrected by Amiram Eldar, Oct 16 2019