A236435 Numerator of product_{k=1..n-1} (1 + 1/prime(k)).

1, 3, 2, 12, 96, 1152, 2304, 41472, 165888, 3981312, 119439360, 3822059520, 7644119040, 321052999680, 1284211998720, 61642175938560, 3328677500682240, 199720650040934400, 399441300081868800, 1597765200327475200, 115039094423578214400, 230078188847156428800, 18406255107772514304000

Offset

1,2

References

G. H. Hardy and E. M. Wright, An Introduction to the Theory of Numbers, 5th ed., Oxford Univ. Press, 1979; Theorem 429.

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..200

J. Sondow and E. Weisstein, MathWorld: Mertens Theorem

Formula

a(n+1) / A236436(n+1) = A072045(n)/A072044(n) / A038110(n+1)/A060753(n+1) because 1+x = (1-x^2) / (1-x).

a(n) / A236436(n) = product_{k=1..n-1} (1 + 1/prime(k)) ~ (6/Pi^2)*exp(gamma)*log(n) as n -> infinity, by Mertens' theorem.

Example

(1 + 1/2)*(1 + 1/3)*(1 + 1/5)*(1 + 1/7) = 96/35 has numerator a(5) = 96.

Mathematica

Numerator@Table[ Product[ 1 + 1/Prime[ k], {k, 1, n-1}], {n, 1, 23}]

Crossrefs

Cf. A038110, A060753, A072044, A072045, A236436.

Sequence in context: A007214 A189736 A025232 * A218566 A125135 A055456

Adjacent sequences: A236432 A236433 A236434 * A236436 A236437 A236438

Keyword

nonn,frac

Author

Jonathan Sondow, Feb 01 2014

Status

approved