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 A064247 #13 Oct 16 2019 11:28:12 %S A064247 30,198,366,576,618,828,1626,2466,2550,3390,4860,4986,5658,6036,6120, %T A064247 6708,6960,7506,12966,13218,13680,15318,16746,18048,18678,19476,20946, %U A064247 21030,21786,22668,23130,23676,23760,25608,26406,26700 %N A064247 Values of m such that N=(am+1)(bm+1)(cm+1) is a 3-Carmichael number (A087788), where a,b,c = 1,2,21. %C A064247 am+1, bm+1, cm+1 are primes and am | (N-1), bm | (N-1), cm |(N-1). %D A064247 Harvey Dubner (harvey(AT)dubner.com), personal communication, Jun 27 2001. %H A064247 Amiram Eldar, <a href="/A064247/b064247.txt">Table of n, a(n) for n = 1..10000</a> %t A064247 CarmichaelNbrQ[n_] := ! PrimeQ@ n && Mod[n, CarmichaelLambda@ n] == 1; Select[ Range@ 30000, PrimeQ[# + 1] && PrimeQ[2# + 1] && PrimeQ[21# + 1] && CarmichaelNbrQ[(# + 1)(2# + 1)(21# + 1)] &] (* _Robert G. Wilson v_, Aug 23 2012 *) %Y A064247 Cf. A087788. %K A064247 nonn %O A064247 1,1 %A A064247 _N. J. A. Sloane_, Sep 23 2001 %E A064247 Offset corrected by _Amiram Eldar_, Oct 16 2019