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 A272338 Numbers such that antisigma(n) mod sigma(n) = phi(n), where antisigma(n) is the sum of the numbers less than n that do not divide n, sigma(n) is the sum of the divisors of n and phi(n) is the Euler totient function of n. 2
 3, 9, 27, 81, 243, 319, 729, 2187, 3615, 6561, 8159, 9807, 19683, 32791, 59049, 103679, 177147, 432864, 531441, 788852, 871215, 1594323, 2779519, 2826863, 2858240, 4782969, 7213536, 10036415, 14348907, 20428863, 24423359, 29036799, 33385279, 43046721 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS A000244 is a subset of this sequence. LINKS Giovanni Resta, Table of n, a(n) for n = 1..73 (terms < 2*10^12) FORMULA Solutions of the equation A024816(n) mod A000203(n) = A000010(n). EXAMPLE 27*28/2 mod sigma(27) = 378 mod 40 = 18 = phi(27). MAPLE with(numtheory): P:=proc(q) local n; for n from 1 to q do if (n*(n+1)/2) mod sigma(n)=phi(n) then print(n); fi; od; end: P(10^6); MATHEMATICA Select[Range[10^5], Function[n, Mod[Total@ First@ #, Total@ Last@ #] == EulerPhi@ n &@ {Complement[Range@ n, #], #} &@ Divisors@ n]] (* Michael De Vlieger, Apr 27 2016 *) CROSSREFS Cf. A000010, A000203, A000244, A024816, A232324, A272337. Sequence in context: A181140 A291007 A038002 * A249019 A216096 A300148 Adjacent sequences: A272335 A272336 A272337 * A272339 A272340 A272341 KEYWORD nonn,easy AUTHOR Paolo P. Lava, Apr 26 2016 EXTENSIONS a(27)-a(34) from Giovanni Resta, May 01 2016 STATUS approved

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Last modified July 12 11:25 EDT 2024. Contains 374245 sequences. (Running on oeis4.)