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A030516
Numbers with 7 divisors. 6th powers of primes.
80
64, 729, 15625, 117649, 1771561, 4826809, 24137569, 47045881, 148035889, 594823321, 887503681, 2565726409, 4750104241, 6321363049, 10779215329, 22164361129, 42180533641, 51520374361, 90458382169, 128100283921
OFFSET
1,1
COMMENTS
These are the numbers p^6 with p prime. - Jorge Coveiro, Apr 13 2004
The n-th number with p divisors is equal to the n-th prime raised to power p-1, where p is prime. - Omar E. Pol, May 06 2008
FORMULA
a(n) = A000040(n)^(7-1) = A000040(n)^6. - Omar E. Pol, May 06 2008
A056595(a(n)) = 3. - Reinhard Zumkeller, Aug 15 2011
Sum_{n>=1} 1/a(n) = P(6) = 0.0170700868... (A085966). - Amiram Eldar, Jul 27 2020
From Amiram Eldar, Jan 23 2021: (Start)
Product_{n>=1} (1 + 1/a(n)) = zeta(6)/zeta(12) = 675675/(691*Pi^6) (A269404).
Product_{n>=1} (1 - 1/a(n)) = 1/zeta(6) = 945/Pi^6 = 1/A013664. (End)
MATHEMATICA
Array[Prime[ # ]^6&, 60] (* Vladimir Joseph Stephan Orlovsky, Dec 14 2009 *)
PROG
(Sage)
[p**6 for p in prime_range(100)]
# Zerinvary Lajos, May 16 2007
(PARI) for(n=1, 1e3, print1(prime(n)^6", ")); \\ Bruno Berselli, Jul 30 2011
(Magma) [NthPrime(n)^6: n in [1..400]]; // Bruno Berselli, Jul 30 2011
(Haskell)
a030516 = (^ 6) . a000040
a030516_list = map (^ 6) a000040_list
-- Reinhard Zumkeller, Jun 03 2015
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved