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 A067130 Numbers n such that sigma(n-1) divides sigma(n+1). 3
 2, 34, 55, 119, 285, 367, 835, 849, 919, 1241, 1505, 1559, 2911, 2914, 2939, 3305, 4149, 4188, 6111, 6903, 7170, 7913, 9360, 10251, 10541, 12566, 15086, 17273, 17759, 17815, 19005, 19689, 19919, 21411, 21462, 24882, 25020, 26610, 28125, 30593, 30789, 31485 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Donovan Johnson, Table of n, a(n) for n = 1..1000 MATHEMATICA Flatten[Position[Partition[DivisorSigma[1, Range[32000]], 3, 1], _?( Divisible[ Last[#], First[#]]&), {1}, Heads->False]]+1 (* Harvey P. Dale, Jan 13 2015 *) PROG (PARI) isok(n) = sigma(n+1) % sigma(n-1) == 0; \\ Michel Marcus, Nov 20 2013 CROSSREFS Cf. A055574. Sequence in context: A124208 A077310 A177051 * A349496 A337397 A263226 Adjacent sequences: A067127 A067128 A067129 * A067131 A067132 A067133 KEYWORD nonn AUTHOR Benoit Cloitre, Feb 18 2002 EXTENSIONS More terms from Michel Marcus, Nov 20 2013 STATUS approved

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Last modified October 2 23:30 EDT 2023. Contains 365841 sequences. (Running on oeis4.)