login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A100481 Greatest prime factor in A095117(n) = greatest prime factor in n + pi(n) where pi(n) is the prime counting function = greatest prime factor in n + A000720(n). 0

%I

%S 1,3,5,3,2,3,11,3,13,7,2,17,19,5,7,11,3,5,3,7,29,5,2,11,17,7,3,37,13,

%T 5,7,43,11,5,23,47,7,5,17,13,3,11,19,29,59,5,31,7,2,13,11,67,23,7,71,

%U 3,73,37,19,11,79,5,3,41,83,7,43,29,11,89,13,23,47,19,3,97,7,11,101,17,103

%N Greatest prime factor in A095117(n) = greatest prime factor in n + pi(n) where pi(n) is the prime counting function = greatest prime factor in n + A000720(n).

%C Conjecture: every prime appears infinitely often in this sequence.

%D Guy, R. K. "The Largest Prime Factor of n." B46 in Unsolved Problems in Number Theory, 2nd ed. New York: Springer-Verlag, p. 101, 1994.

%D Shanks, D. Solved and Unsolved Problems in Number Theory, 4th ed. New York: Chelsea, 1993.

%H Andrew Booker, <a href="http://primes.utm.edu/nthprime/index.php#piofx">The Nth Prime Page</a>.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/PrimeCountingFunction.html">"Prime Counting Function."</a>

%F a(n) = A006530(n + A000720(n)) = greatest prime factor in (n + A000720(n)).

%e a(1) = 1 = A006530(1+0).

%e a(3) = 5 because 3 + pi(3) = p + number of primes less than or equal to 3, of which there are 2 (namely 2 and 3) hence a(3) = 3 + 2 = 5. This is prime, hence equal to its greatest prime factor. a(5) = 2 because 5 + pi(5) = 5 + 3 = 2 * 2 * 2 hence the greatest prime factor is 2.

%Y Cf. A000720, A006530, A095117.

%K easy,nonn

%O 1,2

%A _Jonathan Vos Post_, Nov 22 2004

%E Extended by _Ray Chandler_, Nov 27 2004

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified August 13 04:54 EDT 2020. Contains 336442 sequences. (Running on oeis4.)