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A152000
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a(n) is squarefree and such that for every prime p|a(n) and every prime q|p-1 then q|a(n) holds.
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2
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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
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OFFSET
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1,1
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COMMENTS
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a(n) is a squarefree valid base.
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LINKS
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MAPLE
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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;
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MATHEMATICA
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rad[n_] := Times @@ (First@# & /@ FactorInteger@n);
Select[Range[2, 2530], # == rad[#*EulerPhi[#]] &] (* Jon Maiga, Aug 08 2019 *)
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PROG
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(PARI) is(m) = factorback(factorint(m*eulerphi(m))[, 1]) == m && m > 1; \\ Jinyuan Wang, Aug 08 2019
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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J. Luis, A. Yebra and J. Jimenez Urroz, Nov 19 2008
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EXTENSIONS
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STATUS
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approved
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