A046399 - OEIS

A046399

Smallest squarefree palindrome with exactly n distinct prime factors.

1, 2, 6, 66, 858, 6006, 222222, 22444422, 244868442, 6434774346, 438024420834, 50146955964105, 2415957997595142, 495677121121776594, 22181673755737618122, 5521159517777159511255, 477552751050050157255774

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OFFSET

0,2

COMMENTS

Initial terms of sequences A046392-A046398.

REFERENCES

J.-P. Delahaye, Merveilleux nombres premiers ("Amazing primes"), p. 315, Pour la Science, Paris 2000.

LINKS

Table of n, a(n) for n=0..16.

EXAMPLE

a(4) = 858 = 2*3*11*13.

MATHEMATICA

r[n_] := FromDigits[Reverse[IntegerDigits[n]]]; Do[k = 1; While[r[k] != k || !SquareFreeQ[k] || Length[Select[Divisors[k], PrimeQ]] != n, k++ ]; Print[k], {n, 0, 30}] (* Ryan Propper, Sep 16 2005 *)

CROSSREFS

Cf. A046385, A076886.

Cf. A046392, A046393, A046394, A046395, A046396, A046397, A046398.

Sequence in context: A239696 A335645 A082619 * A082617 A377580 A006517

Adjacent sequences: A046396 A046397 A046398 * A046400 A046401 A046402

KEYWORD

nonn,base,hard,more

AUTHOR

Patrick De Geest, Jun 15 1998

EXTENSIONS

Edited by N. J. A. Sloane, Dec 06 2008 at the suggestion of R. J. Mathar

a(10)-a(13) from Donovan Johnson, Oct 03 2011

a(14)-a(15) from David A. Corneth, Oct 03 2020

a(15) corrected by Daniel Suteu, Feb 05 2023

a(16) from Michael S. Branicky, Feb 08 2023

STATUS

approved