login
A122072
Greatest prime less than 10n.
7
7, 19, 29, 37, 47, 59, 67, 79, 89, 97, 109, 113, 127, 139, 149, 157, 167, 179, 181, 199, 199, 211, 229, 239, 241, 257, 269, 277, 283, 293, 307, 317, 317, 337, 349, 359, 367, 379, 389, 397, 409, 419, 421, 439, 449, 457, 467, 479, 487, 499, 509, 509, 523, 523
OFFSET
1,1
COMMENTS
First repeating terms are 199, 317, 509, 523, 619, 839, 887, 1069, 1129, 1129, 1259, 1327, 1327, 1327, 1409, 1459, 1499, 1637, 1669, 1669, 1709, 1759, 1789, 1847, 1889, 1913, 1951.
a(n) is also the greatest prime factor among composites (A002808) below 20n. For primes of the form 20n + 1, see A141881. - Lekraj Beedassy, Jan 23 2012
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
MATHEMATICA
Table[Prime[PrimePi[10 n]], {n, 54}] (* Jayanta Basu, May 24 2013 *)
PROG
(PARI) a(n)=precprime(10*n) \\ Charles R Greathouse IV, Feb 26 2012
CROSSREFS
Sequence in context: A175376 A175366 A117609 * A261338 A352338 A109355
KEYWORD
nonn,easy
AUTHOR
Zak Seidov, Oct 16 2006
STATUS
approved