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 A077087 Numbers n such that sigma(n+1) = 3 * sigma(n). 3
 1, 1919, 2759, 11219, 27089, 50039, 58463, 100127, 113831, 115289, 120203, 131879, 148511, 233729, 244319, 308039, 461099, 554063, 596447, 1406303, 1486619, 2285519, 2880989, 5138783, 5369111, 5521619, 5736743, 6621383, 7496279, 7683191, 8571527, 8848619 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Donovan Johnson, Table of n, a(n) for n = 1..500 EXAMPLE n=1: sigma[2]/sigma[1]=3/1=3; n=9563231: sigma[n+1]/sigma[n]=31026240/10342080=3 MAPLE A077087:=proc(q) local n; for n from 1 to q do if sigma(n+1)=3*sigma(n) then print(n); fi; od; end: A077087 (10^10); # Paolo P. Lava, Mar 25 2013 MATHEMATICA Do[s=Mod[a=DivisorSigma[1, n+1], b=DivisorSigma[1, n]]; If[Equal[s, 0]&&Equal[a/b, 3], Print[n]], {n, 1, 10000000}] Position[Partition[DivisorSigma[1, Range[9*10^6]], 2, 1], _?(3#[[1]] == #[[2]]&), 1, Heads->False]//Flatten (* Harvey P. Dale, Oct 03 2017 *) CROSSREFS Cf. A000203, A002961, A067081, A077086. Sequence in context: A163863 A251917 A222928 * A179696 A249840 A061374 Adjacent sequences:  A077084 A077085 A077086 * A077088 A077089 A077090 KEYWORD nonn AUTHOR Labos Elemer, Oct 31 2002 STATUS approved

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