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%I #16 Oct 16 2012 17:31:19
%S 7991,4096740829,651,25056,23973,41526,1302,5005333,8175,504,1953,
%T 2919396,13737,1054,2257,1708,11521,22313,16350,123098,1008,1584,3906,
%U 1887,89027,5335754,27474,59550082,2108,1344,4514,1512,3416,2925,5859,494379,44626,1586993,8557
%N Least number m such that phi(m-6n) = phi(m) = phi(m+6n) and m is not divisible by n.
%C a(n) has been computed by _Donovan Johnson_ up to 200, but no values were found below 2*10^11 for n=41, 67, 113, 149, 157, 181.
%H F. Firoozbakht, <a href="http://www.primepuzzles.net/puzzles/puzz_466.htm">Puzzle 466. phi(n-1)=phi(n)=phi(n+1)</a>, in C. Rivera's Primepuzzles.
%H S. W. Graham, J. J. Holt and C. Pomerance, <a href="http://www.math.dartmouth.edu/~carlp/phi.pdf">On the solutions to phi(n) = phi(n+k)</a> Number Theory in Progress, K. Gyory, H. Iwaniec, and J. Urbanowicz, eds., vol. 2, de Gruyter, Berlin and New York, 1999, pp. 867-882.
%H Donovan Johnson and Michel Marcus, <a href="/A217068/a217068.txt">a(n) for n=2 to 200, with missing terms shown as 0.</a>
%Y Cf. A000010, A217006.
%K nonn
%O 2,1
%A _Michel Marcus_, Sep 26 2012
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