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 A066676 Smallest number m such that phi(m) is a multiple of n-th primorial number, the product of first n primes. 4
 3, 7, 31, 211, 2311, 60653, 1023053, 19417793, 446235509, 12939711677, 200560490131, 14841484883609, 608500576478849, 26165522997357677, 1229779567395958169, 65178316970529225209, 3845520700432469775917, 234576762719782814756597, 15716643102168462956621849 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Ray Chandler, Table of n, a(n) for n = 1..25 FORMULA a(n) = Min{x : A000010(x) mod A002110(n) = 0}. EXAMPLE n = 8: a(8) = 19417793, phi(a(8)) = 19199380 = 2*9699690 = 2*2*3*5*7*11*13*17*19. 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 *) CROSSREFS Cf. A000010, A002110, A066674, A066675, A066677, A066678. Sequence in context: A083772 A093441 A087864 * A073917 A030521 A105767 Adjacent sequences:  A066673 A066674 A066675 * A066677 A066678 A066679 KEYWORD nonn AUTHOR Labos Elemer, Dec 19 2001 EXTENSIONS a(9)-a(11) from Donovan Johnson, Oct 12 2011 a(12)-a(13) upper limits from Donovan Johnson confirmed as next terms, a(14)-a(19) added by Ray Chandler, Oct 21 2011 STATUS approved

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Last modified March 28 17:28 EDT 2020. Contains 333090 sequences. (Running on oeis4.)