A242925 Numbers k such that lambda(k) divides Sum_{j=1..k} lambda(j).

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

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