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A152000 a(n) is squarefree and such that for every prime p|a(n) and every prime q|p-1 then q|a(n) holds. 2
2, 6, 10, 30, 34, 42, 78, 102, 110, 114, 170, 210, 222, 330, 390, 410, 438, 510, 514, 546, 570, 582, 654, 714, 798, 930, 978, 1010, 1110, 1158, 1218, 1230, 1326, 1482, 1542, 1554, 1806, 1830, 1870, 1938, 2190, 2310, 2510, 2530 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(n) is a squarefree valid base.

LINKS

Table of n, a(n) for n=1..44.

J. Jimenez Urroz and J. Luis A.Yebra, On the equation a^x=x mod b^n, Journal of Integer Sequences, Vol. 12 (2009), Article 09.8.8

MAPLE

A152000 := proc(n)

    if n = 1 then

        2;

    else

        for a from procname(n-1)+1 do

            if issqrfree(a) then

                pdvs := numtheory[factorset](a) ;

                aworks := true;

                for p in numtheory[factorset](a) do

                    for q in numtheory[factorset](p-1) do

                        if a mod q = 0 then

                            ;

                        else

                            aworks := false;

                        end if;

                    end do:

                end do:

                if aworks then

                    return a;

                end if;

            end if;

        end do:

    end if;

end proc: # R. J. Mathar, Jun 01 2013

CROSSREFS

Cf. A151999.

Sequence in context: A192616 A243393 A102581 * A038042 A032374 A074095

Adjacent sequences:  A151997 A151998 A151999 * A152001 A152002 A152003

KEYWORD

easy,nonn

AUTHOR

J.Luis A.Yebra and J. Jimenez Urroz (yebra(AT)mat.upc.es), Nov 19 2008

EXTENSIONS

Corrected and extended by Michel Marcus, Jun 01 2013

STATUS

approved

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Last modified August 28 20:16 EDT 2015. Contains 261164 sequences.