Search: id:A006511
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%I A006511 M1580
%S A006511 2,6,12,18,30,22,42,60,54,66,46,90,58,62,120,126,150,98,138,94,210,106,
%T A006511 162,174,118,198,240,134,142,270,158,330,166,294,276,282,420,250,206,
%U A006511 318,214,378,242,348,354,462,254,510,262,414,274,278,426,630,298,302
%N A006511 Largest inverse of totient function (A000010): a(n) is the largest x 
               such that phi(x)=m, where m=A002202(n) is the n-th number in the 
               range of phi.
%C A006511 Always even, as phi(2n)=phi(n) when n is odd. - Alain Jacques (thegentleway(AT)bigpond.com), 
               Jun 15 2006
%D A006511 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A006511 J. W. L. Glaisher, Number-Divisor Tables. British Assoc. Math. Tables, 
               Vol. 8, Camb. Univ. Press, 1940, p. 64.
%H A006511 T. D. Noe, <a href="b006511.txt">Table of n, a(n) for n=1..10000</a>
%F A006511 a(n) = A057635(A002202(n)). - T. D. Noe
%t A006511 phiinv[n_, pl_] := Module[{i, p, e, pe, val}, If[pl=={}, Return[If[n==1, 
               {1}, {}]]]; val={}; p=Last[pl]; For[e=0; pe=1, e==0||Mod[n, (p-1)pe/
               p]==0, e++; pe*=p, val=Join[val, pe*phiinv[If[e==0, n, n*p/pe/(p-1)], 
               Drop[pl, -1]]]]; Sort[val]]; phiinv[n_] := phiinv[n, Select[1+Divisors[n], 
               PrimeQ]]; Last/@Select[phiinv/@Range[1, 200], #!={}&] (* phiinv[n, 
               pl] = list of x with phi(x)=n and all prime divisors of x in list 
               pl. phiinv[n] = list of x with phi(x)=n *)
%Y A006511 Cf. A000010, A002202, A002181.
%Y A006511 For records see A036913, A132154, A036912.
%Y A006511 Sequence in context: A162802 A108585 A159793 this_sequence A113274 A036913 
               A117311
%Y A006511 Adjacent sequences: A006508 A006509 A006510 this_sequence A006512 A006513 
               A006514
%K A006511 nonn
%O A006511 1,1
%A A006511 N. J. A. Sloane (njas(AT)research.att.com).

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