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%I #11 Nov 18 2018 00:10:01
%S 2,3,4,6,7,17,34,51,67,167,334,501,667,1667,3334,5001,6667,14286,
%T 16667,33334,50001,66667,166667,333334,500001,666667,1666667,2857143,
%U 3333334,5000001,6666667,16666667,33333334,50000001,66666667
%N Numbers k with the property that k divides one of the concatenations (k-1)(k-2) or (k-2)(k-1).
%C No more terms through 10^8. - _Ryan Propper_, Oct 11 2005
%e 6 and 7 are terms: 6 divides 54, 7 divides 56.
%t c[r_, s_] := ToExpression[ToString[r] <> ToString[s]]; Do[k = c[n-1, n-2]; m = c[n-2, n-1]; If[Mod[k, n] == 0 || Mod[m, n] == 0, Print[n]], {n, 2, 10^8}] (* _Ryan Propper_, Oct 11 2005 *)
%t ccQ[n_]:=Module[{id1=IntegerDigits[n-1],id2=IntegerDigits[n-2]},Divisible[ FromDigits[ Join[id1,id2]],n]||Divisible[FromDigits[Join[id2,id1]],n]]; Select[Range[2,67000000],ccQ] (* _Harvey P. Dale_, Jun 18 2012 *)
%K base,nonn
%O 1,1
%A _Amarnath Murthy_, Nov 03 2002
%E More terms from _Ray G. Opao_, Sep 28 2005
%E 2 more terms from _Ryan Propper_, Oct 11 2005
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