The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 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). 0
 3, 9, 16, 31, 68, 149, 314, 724, 1670, 4063 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Conjecture:  A055553(n)/a(n) has a limit strictly smaller than 1 as n tends to infinity. LINKS 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified February 27 04:56 EST 2020. Contains 332299 sequences. (Running on oeis4.)