OFFSET
1,1
COMMENTS
Numbers of the forms p^48 and p^6*q^6, where p and q are distinct primes.
LINKS
T. D. Noe, Table of n, a(n) for n = 1..1000
OEIS Wiki, Index entries for number of divisors
FORMULA
A000005(a(n)) = 49.
Sum_{n>=1} 1/a(n) = (P(6)^2 - P(12))/2 + P(48) = 0.0000226806..., where P is the prime zeta function. - Amiram Eldar, Jul 03 2022
MATHEMATICA
Select[Range[100000000], DivisorSigma[0, #]==48&] (* Vladimir Joseph Stephan Orlovsky, May 06 2011 *)
PROG
(Haskell)
a175755 n = a175755_list !! (n-1)
a175755_list = m (map (^ 48) a000040_list) (map (^ 6) a006881_list) where
m xs'@(x:xs) ys'@(y:ys) | x < y = x : m xs ys'
| otherwise = y : m xs' ys
-- Reinhard Zumkeller, Nov 29 2011
(PARI) is(n)=numdiv(n)==49 \\ Charles R Greathouse IV, Jun 19 2016
CROSSREFS
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Aug 27 2010
EXTENSIONS
Extended by T. D. Noe, May 08 2011
STATUS
approved