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A078550
Non-balanced numbers in A015774.
6
38, 46, 54, 87, 95, 114, 126, 134, 135, 138, 147, 161, 174, 182, 184, 209, 215, 216, 222, 230, 258, 285, 294, 297, 299, 315, 322, 398, 402, 414, 430, 437, 455, 456, 483, 540, 546, 551, 552, 598, 609, 623, 627, 632, 635, 644, 645, 670, 690, 762, 783, 805
OFFSET
1,1
LINKS
FORMULA
sigma_15(a(n)) mod phi(a(n)) = 0; sigma(a(n)) mod phi(a(n)) <> 0.
MATHEMATICA
q[n_] := Sign[Mod[DivisorSigma[{1, 15}, 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, 15) % phi); } \\ Amiram Eldar, Apr 11 2024
KEYWORD
nonn
AUTHOR
Labos Elemer, Dec 05 2002
EXTENSIONS
Name corrected by Amiram Eldar, Apr 11 2024
STATUS
approved