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A066676
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Smallest number m such that phi(m) is a multiple of n-th primorial number, the product of first n primes.
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2
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3, 7, 31, 211, 2311, 60653, 1023053, 19417793, 446235509, 12939711677, 200560490131, 14841484883609, 608500576478849, 26165522997357677, 1229779567395958169, 65178316970529225209, 3845520700432469775917, 234576762719782814756597, 15716643102168462956621849
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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LINKS
| Ray Chandler, Table of n, a(n) for n = 1..25
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FORMULA
| a[n] = Min{x : Mod[A000010(x), A002110(n)] = 0}
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EXAMPLE
| n = 8: a[8] = 19417793, phi(a(8)) = 19199380 = 2*9699690 = 2*2*3*5*7*11*13*17*19.
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MATHEMATICA
| nmax = 25;
A066676 = {};
pm = 1;
Do[
pm *= Prime[n];
sol = 0;
If[PrimeQ[pm + 1],
sol = pm + 1;
,
sd = Select[Divisors[pm/2], # <= Sqrt[pm/2] &];
Do[
f1 = sd[[i]];
f2 = pm/2/f1;
If[PrimeQ[2 f1 + 1] && PrimeQ[2 f2 + 1],
sol = (2 f1 + 1)*(2 f2 + 1);
Break[];
];
, {i, Length[sd], 1, -1}];
];
AppendTo[A066676, sol];
Print[{n, sol}];
, {n, nmax}];
A066676 (* Ray Chandler, Oct 21 2011 *)
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CROSSREFS
| Cf. A000010, A002110, A066674-A066678.
Sequence in context: A083772 A093441 A087864 * A073917 A030521 A105767
Adjacent sequences: A066673 A066674 A066675 * A066677 A066678 A066679
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KEYWORD
| nonn
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu), Dec 19 2001
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EXTENSIONS
| a(9)-a(11) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Oct 12 2011
a(12)-a(13) upper limits from Donovan Johnson confirmed as next terms, a(14)-a(19) added by Ray Chandler (rayjchandler(AT)sbcglobal.net), Oct 21 2011
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