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A078559
Numerator of Product_{i=1..n} (p_i+1)/(p_i-1) where p_i is the i-th prime.
2
3, 6, 9, 12, 72, 84, 189, 21, 252, 270, 288, 304, 1596, 152, 3648, 49248, 295488, 1526688, 17302464, 622888704, 640191168, 1707176448, 10243058688, 23046882048, 23527025424, 599939148312, 47054050848, 2540918745792
OFFSET
1,1
REFERENCES
R. K. Guy, Unsolved Problems in Number Theory, B48.
LINKS
Robert Israel, Table of n, a(n) for n = 1..1701 (b-file corrected by Georg Fischer, Jan 16 2019)
FORMULA
a(n) = A054640(n)/A078558(n).
MAPLE
Q:= 1: p:= 1:
for n from 1 to 100 do
p:= nextprime(p);
Q:= Q * (p+1)/(p-1);
A[n]:= numer(Q);
od:
seq(A[i], i=1..100); # Robert Israel, May 11 2018
MATHEMATICA
Numerator[Table[Product[(Prime[i] + 1)/(Prime[i] - 1), {i, n}], {n, 30}]] (* Alonso del Arte, Aug 23 2011 *)
PROG
(PARI) a(n) = numerator(prod(i=1, n, (prime(i)+1)/(prime(i)-1))); \\ Michel Marcus, May 11 2018
CROSSREFS
Denominators are in A078560.
Sequence in context: A072179 A065811 A061514 * A317557 A338763 A159908
KEYWORD
nonn,frac
AUTHOR
Labos Elemer, Dec 06 2002
EXTENSIONS
Improved definition from Franklin T. Adams-Watters, Dec 02 2005
STATUS
approved