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A077801
Non-balanced numbers in A015767.
6
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
1,1
LINKS
FORMULA
sigma_9(a(n)) mod phi(a(n)) = 0; sigma(a(n)) mod phi(a(n)) <> 0.
MATHEMATICA
q[n_] := Sign[Mod[DivisorSigma[{1, 9}, n], EulerPhi[n]]] == {1, 0}; Select[Range[1000], q] (* Amiram Eldar, Apr 11 2024 *)
PROG
(PARI) is(n) = {my(f = factor(n), phi = eulerphi(f)); (sigma(f) % phi) && !(sigma(f, 9) % phi); } \\ Amiram Eldar, Apr 11 2024
KEYWORD
nonn
AUTHOR
Labos Elemer, Dec 05 2002
STATUS
approved