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 A194507 a(n) = y is the unique solution to y*phi(y) = A082473(n). 5
 1, 2, 3, 4, 6, 5, 8, 10, 7, 12, 9, 14, 18, 11, 15, 16, 13, 20, 24, 22, 30, 21, 17, 26, 28, 19, 36, 27, 25, 42, 23, 32, 34, 40, 33, 38, 48, 29, 35, 44, 31, 39, 60, 54, 50, 46, 45, 52, 66, 37, 56, 58, 51, 41, 70, 72, 43, 62, 78, 84, 64, 57, 49, 90, 47, 68, 55, 63, 80 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS The permutation which rearranges the terms of A002618 into ascending order. - Antti Karttunen, Sep 28 2019 LINKS Antti Karttunen, Table of n, a(n) for n = 1..20001 FORMULA From Antti Karttunen, Sep 28 2019: (Start) a(n) = A327172(A082473(n)). A002618(a(n)) = A082473(n). (End) EXAMPLE a(6) = 5 because 5*phi(5) = 20 = A082473(6). MATHEMATICA Block[{nn = 3000, s, t}, s = Array[EulerPhi[#] (Sqrt@ # /. (c_: 1) a_^(b_: 0) :> (c a^b)^2) &, nn]; t = TakeWhile[Union@ s, # <= nn &]; Map[Block[{y = 1}, While[y EulerPhi@ y != #, y++]; y] &, t]] (* Michael De Vlieger, Sep 29 2019, after Bill Gosper at A007913 *) PROG (PARI) up_to = 105; A327172(n) = { fordiv(n, d, if(eulerphi(d)*d == n, return(d))); (0); }; A194507list(up_to) = { my(v=vector(up_to), k=1); for(n=1, oo, if((v[k]=A327172(n))>0, k++); if(k>up_to, return(v))); }; v194507 = A194507list(up_to); A194507(n) = v194507[n]; \\ Antti Karttunen, Sep 28 2019 CROSSREFS Cf. A002618, A082473, A327173 (inverse permutation). Nonzero terms in A327172, in the order of appearance. Sequence in context: A257471 A053212 A095424 * A118316 A197756 A080738 Adjacent sequences:  A194504 A194505 A194506 * A194508 A194509 A194510 KEYWORD nonn AUTHOR Franz Vrabec, Aug 27 2011 STATUS approved

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Last modified April 14 21:21 EDT 2021. Contains 342962 sequences. (Running on oeis4.)