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Search: id:A006511
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| A006511 |
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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.
(Formerly M1580)
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+0
8
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| 2, 6, 12, 18, 30, 22, 42, 60, 54, 66, 46, 90, 58, 62, 120, 126, 150, 98, 138, 94, 210, 106, 162, 174, 118, 198, 240, 134, 142, 270, 158, 330, 166, 294, 276, 282, 420, 250, 206, 318, 214, 378, 242, 348, 354, 462, 254, 510, 262, 414, 274, 278, 426, 630, 298, 302
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Always even, as phi(2n)=phi(n) when n is odd. - Alain Jacques (thegentleway(AT)bigpond.com), Jun 15 2006
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
J. W. L. Glaisher, Number-Divisor Tables. British Assoc. Math. Tables, Vol. 8, Camb. Univ. Press, 1940, p. 64.
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LINKS
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T. D. Noe, Table of n, a(n) for n=1..10000
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FORMULA
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a(n) = A057635(A002202(n)). - T. D. Noe
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MATHEMATICA
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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 *)
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CROSSREFS
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Cf. A000010, A002202, A002181.
For records see A036913, A132154, A036912.
Sequence in context: A162802 A108585 A159793 this_sequence A113274 A036913 A117311
Adjacent sequences: A006508 A006509 A006510 this_sequence A006512 A006513 A006514
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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