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A067243 Numbers m such that sigma(m+1)+sigma(m-1) = 6*phi(m). 1
34, 55, 141, 322, 664, 988, 1149, 1505, 2230, 2631, 2906, 2912, 8559, 11194, 18215, 18754, 57104, 60599, 62881, 64604, 78759, 81580, 96304, 96944, 97220, 98944, 99164, 126520, 182495, 192417, 200123, 220661, 255968, 272405, 275931, 354032, 392755, 422956, 426095, 444962 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
MATHEMATICA
Select[Range[200000], DivisorSigma[1, #-1]+DivisorSigma[1, #+1] == 6*EulerPhi[#]&] (* Harvey P. Dale, May 07 2014 *)
PROG
(PARI) isok(m) = (m>1) && (sigma(m+1)+sigma(m-1) == 6*eulerphi(m)); \\ Michel Marcus, Feb 17 2021
CROSSREFS
Sequence in context: A305061 A051969 A241520 * A171668 A259676 A227304
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Feb 20 2002
EXTENSIONS
More terms from Michel Marcus, Feb 17 2021
STATUS
approved

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Last modified June 19 15:41 EDT 2024. Contains 373503 sequences. (Running on oeis4.)