A077801 Non-balanced numbers in A015767.

38, 54, 87, 95, 114, 126, 135, 147, 174, 182, 209, 215, 216, 222, 258, 266, 285, 294, 297, 315, 342, 378, 430, 447, 455, 456, 494, 518, 540, 546, 551, 609, 627, 632, 635, 645, 654, 665, 702, 762, 783, 798, 836, 894, 899, 945, 957, 1015, 1022, 1032, 1064

Offset: 1

Author

Labos Elemer, Dec 05 2002

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000010, A000203, A013957, A015767, A020492, A078539.

Cf. A074866, A074868, A077803, A078544, A078549, A078550.

Programs

Mathematica

q[n_] := Sign[Mod[DivisorSigma[{1, 9}, n], EulerPhi[n]]] == {1, 0}; Select[Range[1000], q] (* Amiram Eldar, Apr 11 2024 *)

PARI

is(n) = {my(f = factor(n), phi = eulerphi(f)); (sigma(f) % phi) && !(sigma(f, 9) % phi);} \\ Amiram Eldar, Apr 11 2024

Formula

sigma_9(a(n)) mod phi(a(n)) = 0; sigma(a(n)) mod phi(a(n)) <> 0.