A122072 Greatest prime less than 10*n.

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 20*n. For primes of the form 20*n + 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

Adjacent sequences: A122069 A122070 A122071 * A122073 A122074 A122075

Keyword

nonn,easy

Author

Zak Seidov, Oct 16 2006

Status

approved