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A215285 n such that sum_{k=1..n} (n - k | k) = phi(n), where (i|j) is the Kronecker symbol and phi(n) is the Euler totient function. 2

%I

%S 1,2,3,4,6,9,16,36,64,100,144,196,256,324,400,484,576,676,784,900,

%T 1024,1156,1296,1444,1600,1764,1936,2116,2304,2500,2704,2916,3136,

%U 3364,3600,3844,4096,4356,4624,4900,5184,5476,5776,6084,6400,6724,7056,7396,7744

%N n such that sum_{k=1..n} (n - k | k) = phi(n), where (i|j) is the Kronecker symbol and phi(n) is the Euler totient function.

%C n is in this sequence if and only if sum_{k=1..n} (n-k|k) = sum_{k=1..n} |(n-k|k)|.

%t Reap[ Do[ If[ Sum[ KroneckerSymbol[n - k, k], {k, 1, n}] == EulerPhi[n], Print[n]; Sow[n]], {n, 1, 8000}]][[2, 1]] (* _Jean-Fran├žois Alcover_, Jul 29 2013 *)

%o (Sage)

%o def A215200_row(n): return [kronecker_symbol(n-k, k) for k in (1..n)]

%o [n for n in (1..1000) if sum(A215200_row(n)) == euler_phi(n)]

%Y Cf. A000010, A215200, A215283, A215284.

%K nonn

%O 1,2

%A _Peter Luschny_, Aug 07 2012

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Last modified October 23 10:17 EDT 2021. Contains 348211 sequences. (Running on oeis4.)