%I A001274 M2999 N1215
%S A001274 1,3,15,104,164,194,255,495,584,975,2204,2625,2834,3255,3705,5186,5187,
%T A001274 10604,11715,13365,18315,22935,25545,32864,38804,39524,46215,48704,49215,
               49335,
%U A001274 56864,57584,57645,64004,65535,73124,105524,107864,123824,131144,164175,
               184635
%N A001274 Numbers n such that phi(n) = phi(n+1).
%C A001274 Unlike totients, cototient[x+1] = cototient[x] never holds - except 2-Phi[2] 
               = 3-Phi[3] = 1 - because cototient[x] congruent x modulo 2. - Labos 
               E. (labos(AT)ana.sote.hu), Aug 08 2001
%D A001274 R. Baillie, Table of phi(n) = phi(n+1), Math. Comp., 30 (1976), 189-190.
%D A001274 J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 15, pp 5, Ellipses, 
               Paris 2008.
%D A001274 R. K. Guy, Unsolved Problems Number Theory, Sect. B36.
%D A001274 V. L. Klee, Jr., Some remarks on Euler's totient function, Amer. Math. 
               Monthly, 54 (1947), 332.
%D A001274 M. Lal and P. Gillard, On the equation phi(n) = phi(n+k), Math. Comp., 
               26 (1972), 579-583.
%D A001274 K. Miller, Solutions of phi(n) = phi(n+1) for 1 <= n <= 500000. Unpublished, 
               1972. [ Cf. Math. Comp., Vol. 27, p. 447, 1973 ].
%D A001274 L. Moser, Some equations involving Euler's totient function, Amer. Math. 
               Monthly, 56 (1949), 22-23.
%D A001274 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 
               (includes this sequence).
%D A001274 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%H A001274 T. D. Noe, <a href="b001274.txt">Table of n, a(n) for n=1..2567</a> (terms 
               less than 10^11)
%e A001274 phi(3) = phi(4) = 2, phi(15) = phi(16) = 8.
%Y A001274 Cf. A000010, A001494, A051953.
%Y A001274 Cf. A003276.
%Y A001274 Cf. A003275
%Y A001274 Sequence in context: A135903 A123184 A079486 this_sequence A139766 A003276 
               A136092
%Y A001274 Adjacent sequences: A001271 A001272 A001273 this_sequence A001275 A001276 
               A001277
%K A001274 nonn,easy,nice
%O A001274 1,2
%A A001274 N. J. A. Sloane (njas(AT)research.att.com).
%E A001274 More terms from David W. Wilson (davidwwilson(AT)comcast.net)