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.

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

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-François 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