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 A242925 Numbers k such that lambda(k) divides Sum_{j=1..k} lambda(j). 1
 1, 2, 3, 4, 6, 7, 8, 11, 12, 14, 15, 16, 18, 19, 20, 24, 30, 31, 34, 40, 42, 44, 60, 72, 80, 83, 130, 132, 136, 195, 208, 218, 232, 254, 258, 259, 260, 264, 272, 276, 305, 306, 408, 420, 440, 464, 504, 560, 585, 586, 594, 595, 609, 624, 636, 715, 819, 840 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Numbers k such that A162578(k)/A002322(k) = Sum_{j=1..k}A002322(j)/ A002322(k) is an integer where lambda(k) is the Carmichael lambda function (A002322). The corresponding integers are 1, 2, 2, 3, 6, 3, 10, 4, 21, 10, 16, 17, 15, 6, 28, 76, 60, 9, 19, 98, ... LINKS G. C. Greubel, Table of n, a(n) for n = 1..1500 EXAMPLE 12 is in the sequence because A162578(12)/A002322(12) = 42/2 = 21 is an integer. MAPLE with(numtheory):nn:=2000:for n from 1 to nn do:p:=lambda(n): s:=sum('lambda(j)', 'j'=1..n):if irem(s, p)=0 then printf(`%d, `, n):else fi:od: MATHEMATICA nn = 2000; sums = Accumulate[CarmichaelLambda[Range[nn]]]; Select[Range[nn], Mod[sums[[#]], CarmichaelLambda[#]] == 0 &] CROSSREFS Cf. A194855, A002322, A162578. Sequence in context: A235035 A235045 A235032 * A336444 A214913 A052499 Adjacent sequences: A242922 A242923 A242924 * A242926 A242927 A242928 KEYWORD nonn AUTHOR Michel Lagneau, May 26 2014 STATUS approved

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Last modified August 10 23:32 EDT 2024. Contains 375059 sequences. (Running on oeis4.)