%I A001837 M5406 N2349
%S A001837 157,262,367,412,472,487,577,682,787,877,892,907,997,1072,
%T A001837 1207,1237,1312,1402,1522,1567,1627,1657,1732,1852,1942,2047,
%U A001837 2062,2152,2194,2257,2362,2437,2467,2557,2572,2677,2722,2782
%N A001837 Numbers n such that phi(2n+1) < phi(2n).
%C A001837 Greg Martin (gerg(AT)math.toronto.edu) writes: I recently calculated 
               the smallest solution of phi(30n+1) < phi(30n) (Amer. Math. Monthly 
               106 (1999), no. 5, 449-451); it has 1116 digits.
%D A001837 J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 157, p. 51, Ellipses, 
               Paris 2008.
%D A001837 V. L. Klee, Jr., Some remarks on Euler's totient function, Amer. Math. 
               Monthly, 54 (1947), 332.
%D A001837 J. O. Shallit, personal communication.
%D A001837 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 
               (includes this sequence).
%D A001837 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%p A001837 with(numtheory,phi); f := proc(n) if phi(2*n+1) < phi(2*n) then RETURN(n) 
               fi end;
%t A001837 Select[ Range[4000], EulerPhi[2# + 1] < EulerPhi[2# ] & ]
%Y A001837 Cf. A000010.
%Y A001837 Sequence in context: A142231 A020356 A142367 this_sequence A142581 A140625 
               A142874
%Y A001837 Adjacent sequences: A001834 A001835 A001836 this_sequence A001838 A001839 
               A001840
%K A001837 nonn
%O A001837 1,1
%A A001837 N. J. A. Sloane (njas(AT)research.att.com).