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%I #18 Dec 06 2024 07:00:54
%S 34,55,141,322,664,988,1149,1505,2230,2631,2906,2912,8559,11194,18215,
%T 18754,57104,60599,62881,64604,78759,81580,96304,96944,97220,98944,
%U 99164,126520,182495,192417,200123,220661,255968,272405,275931,354032,392755,422956,426095,444962
%N Numbers m such that sigma(m+1)+sigma(m-1) = 6*phi(m).
%H Amiram Eldar, <a href="/A067243/b067243.txt">Table of n, a(n) for n = 1..320</a>
%t Select[Range[200000],DivisorSigma[1,#-1]+DivisorSigma[1,#+1] == 6*EulerPhi[#]&] (* _Harvey P. Dale_, May 07 2014 *)
%o (PARI) isok(m) = (m>1) && (sigma(m+1)+sigma(m-1) == 6*eulerphi(m)); \\ _Michel Marcus_, Feb 17 2021
%Y Cf. A000010 (phi), A000203 (sigma), A067242.
%K nonn
%O 1,1
%A _Benoit Cloitre_, Feb 20 2002
%E More terms from _Michel Marcus_, Feb 17 2021