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 A216394 Number of values of k for which phi(k) is a permutation of decimal digits of k, for 2^(n-1) < k < 2^n. 2
 1, 0, 0, 0, 1, 1, 0, 0, 2, 0, 0, 3, 11, 2, 13, 21, 26, 49, 91, 186, 108, 335, 937, 500, 1681, 4208, 4156 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,9 LINKS FORMULA a(n) = # { k in A115921 | 2^(n-1) < k < 2^n }. - M. F. Hasler, Feb 24 2014 EXAMPLE a(14) = 2 because the values of k satisfying the condition for 2^13 < k < 2^14 are {8541, 8982}. - V. Raman, Feb 18 2014 PROG (PARI) a(n)=sum(k=2^(n-1), 2^n, vecsort(digits(k)) == vecsort(digits(eulerphi(k)))) \\ V. Raman, Feb 18 2014, based on edits by M. F. Hasler (Python) from sympy import totient def A216394(n): ....if n == 1: ........return 1 ....c = 0 ....for i in range(2**(n-1)+1, 2**n): ........s1, s2 = sorted(str(i)), sorted(str(totient(i))) ........if len(s1) == len(s2) and s1 == s2: ............c += 1 ....return c # Chai Wah Wu, Jul 23 2015 CROSSREFS Cf. A115921, A000010. Sequence in context: A244120 A277536 A269159 * A028590 A074644 A321256 Adjacent sequences:  A216391 A216392 A216393 * A216395 A216396 A216397 KEYWORD nonn,base,more AUTHOR V. Raman, Sep 06 2012 STATUS approved

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Last modified September 17 06:52 EDT 2019. Contains 327119 sequences. (Running on oeis4.)