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 A039770 Numbers n such that phi(n) is a perfect square. 37
 1, 2, 5, 8, 10, 12, 17, 32, 34, 37, 40, 48, 57, 60, 63, 74, 76, 85, 101, 108, 114, 125, 126, 128, 136, 160, 170, 185, 192, 197, 202, 204, 219, 240, 250, 257, 273, 285, 292, 296, 304, 315, 364, 370, 380, 394, 401, 432, 438, 444, 451, 456, 468, 489, 504, 505 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS A004171 is a subsequence because phi(2^(2n+1)) = (2^n)^2. - Enrique Pérez Herrero, Aug 25 2011 REFERENCES D. M. Burton, Elementary Number Theory, Allyn and Bacon Inc., Boston MA, 1976, p. 141. LINKS T. D. Noe, Table of n, a(n) for n = 1..10000 W. D. Banks, J. B. Friedlander, C. Pomerance and I. E. Shparlinski, Multiplicative structure of values of the Euler function, in High Primes and Misdemeanours: Lectures in Honour of the Sixtieth Birthday of Hugh Cowie Williams (A. Van der Poorten, ed.), Fields Inst. Comm. 41 (2004), pp. 29-47. P. Pollack and C. Pomerance, Square values of Euler's function, submitted for publication. Bernard Schott, Subfamilies and subsequences FORMULA a(n) seems to be asymptotic to c*n^(3/2) with 1

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Last modified April 11 00:03 EDT 2021. Contains 342877 sequences. (Running on oeis4.)