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

1,1

Links

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

Formula

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

Mathematica

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

Prog

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

Crossrefs

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

Sequence in context: A043955 A341172 A077801 * A116243 A098126 A244313

Adjacent sequences: A078541 A078542 A078543 * A078545 A078546 A078547

Keyword

nonn

Author

Labos Elemer, Dec 05 2002

Status

approved