

A290497


Carmichael numbers with a record number of aliquot divisors that are also Carmichael numbers.


1



561, 63973, 31146661, 509033161, 84127131361, 11985185775745, 712484043821641, 24349841028259201, 53545320695780641, 141125066711098561, 16223841675726285601
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OFFSET

1,1


COMMENTS

The number of aliquot divisors is 0, 1, 2, 5, 7, 8, 10, 11, 17, 20, 26, ...
The terms were calculated using Pinch's tables of Carmichael numbers (see link below).


LINKS

Table of n, a(n) for n=1..11.
R. G. E. Pinch, Tables relating to Carmichael numbers.


EXAMPLE

509033161 is in the sequence since it is a Carmichael number, and 5 of its divisors are also Carmichael numbers (1729, 63973, 126217, 188461 and 294409), more than for any smaller Carmichael number.


MATHEMATICA

A002997 = Cases[Range[1, 100000, 2], n_ /; Mod[n, CarmichaelLambda[n]] == 1 && ! PrimeQ[n]]; carmichaelQ[n_] := Not[PrimeQ[n]] && Divisible[n  1, CarmichaelLambda[n]]; numSol[n_] := Module[{m = 0}, ds = Divisors[n]; Do[d = ds[[k]]; If[! carmichaelQ[d], Continue[]]; m++, {k, 2, Length[ds]  1}]; m]; numSolmax = 1; seq = {}; Do[n = A002997[[j]]; m = numSol[n]; If[m > numSolmax, AppendTo[seq, n]; numSolmax = m], {j, 1, Length[A002997]}]; seq


CROSSREFS

Cf. A002997.
Sequence in context: A258801 A329460 A097061 * A258839 A213867 A139089
Adjacent sequences: A290494 A290495 A290496 * A290498 A290499 A290500


KEYWORD

nonn,more


AUTHOR

Amiram Eldar, Aug 04 2017


EXTENSIONS

a(11) from Amiram Eldar, Jun 29 2019


STATUS

approved



