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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
1, 2, 3, 4, 6, 9, 16, 36, 64, 100, 144, 196, 256, 324, 400, 484, 576, 676, 784, 900, 1024, 1156, 1296, 1444, 1600, 1764, 1936, 2116, 2304, 2500, 2704, 2916, 3136, 3364, 3600, 3844, 4096, 4356, 4624, 4900, 5184, 5476, 5776, 6084, 6400, 6724, 7056, 7396, 7744 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

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

LINKS

Table of n, a(n) for n=1..49.

MATHEMATICA

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 *)

PROG

(Sage)

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

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

CROSSREFS

Cf. A000010, A215200, A215283, A215284.

Sequence in context: A256774 A213682 A103481 * A275173 A295394 A081419

Adjacent sequences:  A215282 A215283 A215284 * A215286 A215287 A215288

KEYWORD

nonn

AUTHOR

Peter Luschny, Aug 07 2012

STATUS

approved

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Last modified September 26 13:19 EDT 2021. Contains 347668 sequences. (Running on oeis4.)