A074868 Non-balanced numbers in A015765.

295, 590, 767, 885, 1038, 1416, 1534, 1589, 1770, 2065, 2301, 2422, 3178, 3186, 3245, 3304, 3448, 3540, 4130, 4602, 4767, 5192, 5230, 5448, 5516, 5605, 6195, 6291, 6356, 6490, 6574, 6860, 7266, 7945, 7965, 8236, 8260, 8437, 8968, 9145, 9204, 9342

Offset

1,1

Links

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

Formula

sigma_7(a(n)) mod phi(a(n)) = 0; sigma(a(n)) mod phi(a(n)) <> 0.

Mathematica

q[n_] := Sign[Mod[DivisorSigma[{1, 7}, n], EulerPhi[n]]] == {1, 0}; Select[Range[10000], q] (* Amiram Eldar, Apr 11 2024 *)

Prog

(PARI) is(n) = {my(f = factor(n), phi = eulerphi(f)); (sigma(f) % phi) && !(sigma(f, 7) % phi); } \\ Amiram Eldar, Apr 11 2024

Crossrefs

Cf. A000010, A000203, A013955, A015765, A020492, A078539.

Cf. A074866, A077801, A077803, A078544, A078549, A078550.

Sequence in context: A289345 A063049 A131274 * A277338 A252083 A279052

Adjacent sequences: A074865 A074866 A074867 * A074869 A074870 A074871

Keyword

nonn

Author

Labos Elemer, Dec 05 2002

Status

approved