A232167 - OEIS

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A232167

Number of composite integers k less than 10^n such that lambda(k) divides 2k-2, where lambda is the Carmichael lambda function (A002322).

3, 9, 16, 31, 68, 149, 314, 724, 1670, 4063

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OFFSET

1,1

COMMENTS

Conjecture: A055553(n)/a(n) has a limit strictly smaller than 1 as n tends to infinity.

LINKS

Table of n, a(n) for n=1..10.

J. M. Grau and A. Oller-Marcén, On the congruence sum_{j=1}^{n-1} j^{k(n-1)} == -1 (mod n). k-strong Giuga and k-Carmichael numbers, arXiv:1311.3522 [math.NT], 2013.

MATHEMATICA

For[k = 4; cnt = 0, True, k++, If[CompositeQ[k] && Divisible[2k-2, CarmichaelLambda[k]], cnt++]; If[IntegerQ[n = Log[10, k+1]], Print[n, " ", cnt]]]; (* Jean-François Alcover, Feb 16 2019 *)

CROSSREFS

Cf. A002322, A055553.

Sequence in context: A212870 A306447 A257034 * A058538 A197531 A117108

Adjacent sequences: A232164 A232165 A232166 * A232168 A232169 A232170

KEYWORD

nonn,more

AUTHOR

José María Grau Ribas, Mar 02 2014

EXTENSIONS

a(8)-a(10) from Giovanni Resta, Mar 03 2014

STATUS

approved