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%I #24 Mar 31 2021 02:36:21
%S 15,21,33,39,51,57,65,69,85,87,91,93,111,123,129,133,141,145,159,177,
%T 183,185,201,205,213,217,219,237,249,259,265,267,291,301,303,305,309,
%U 321,327,339,341,365,381,393,411,417,427,445,447,451,453,469,471,481
%N Odd numbers m = p*q such that p and q are distinct primes and (p-1) divides (q-1).
%C Neither p nor q can equal 2, i.e., 2 is not a permissible prime here. - _Harvey P. Dale_, May 04 2011
%H Amiram Eldar, <a href="/A177516/b177516.txt">Table of n, a(n) for n = 1..10000</a>
%e (3 - 1) divides (5 - 1), so 3 * 5 = 15 is in this sequence.
%e (5 - 1) divides (17 - 1) so 5 * 17 = 85 is in this sequence.
%e (5 - 1) does not divide (19 - 1), so 5 * 19 = 95 is not in this sequence.
%t Table[If[i < j && IntegerQ[(Prime[j] - 1)/(Prime[i] - 1)], Prime[j] * Prime[i]],{i, 2, 100}, {j, 2, 100}] // Flatten // Union
%t Union[Times@@@Select[Subsets[Prime[Range[2, 100]], {2}], Divisible[Last[#] - 1, First[#] - 1] &]] (* _Harvey P. Dale_, May 04 2011 *)
%Y Cf. A046388.
%K nonn
%O 1,1
%A _José María Grau Ribas_, Dec 11 2010
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