A078544 Non-balanced numbers in A015761.

38, 54, 87, 95, 114, 126, 135, 147, 174, 182, 209, 215, 216, 222, 258, 285, 294, 297, 315, 430, 455, 456, 540, 546, 551, 609, 627, 632, 635, 645, 762, 783, 836, 899, 957, 1015, 1032, 1102, 1107, 1118, 1140, 1188, 1211, 1218, 1270, 1290, 1330, 1343, 1349

Offset: 1

Author

Labos Elemer, Dec 05 2002

Keywords

• nonn

Links

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

Crossrefs

Cf. A015761, A020492, A000005, A000010, A078539.

Programs

Mathematica

Select[Range[1350], Divisible[DivisorSigma[3, #],(phi = EulerPhi[#])] && !Divisible[DivisorSigma[1, #], phi] &] (* Amiram Eldar, Jun 23 2019 *)

PARI

isok(k) = my(phi=eulerphi(k)); ((sigma(k, 3) % phi) == 0) && (sigma(k) % phi); \\ Michel Marcus, Jun 23 2019

Formula

Mod[sigma[3, a(n)], phi[a(n)]]=0; Mod[sigma[1, a(n)], phi[a(n)]]><0.