A136153 Composites one larger than a prime, with exactly four distinct prime factors.

390, 420, 462, 510, 570, 660, 770, 798, 840, 858, 930, 1020, 1050, 1092, 1110, 1218, 1230, 1260, 1290, 1302, 1320, 1410, 1428, 1430, 1482, 1554, 1560, 1610, 1638, 1710, 1722, 1848, 1890, 1914, 1932, 1950, 1974, 1980, 2030, 2040, 2070, 2090, 2100, 2130

Offset: 1

Author

Enoch Haga, Dec 16 2007

Keywords

• easy
• nonn

Examples

			a(0)=390 because 30 follows the prime 29 and has four prime factors 2, 3, 5 and 13.
		

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..2000

Crossrefs

Cf. A136151, A136152, A136154, A136155.

Programs

Mathematica

Select[Prime[Range[400]]+1,PrimeNu[#]==4&] (* Harvey P. Dale, Aug 15 2021 *)

PARI

isok(n) = (omega(n)==4) && isprime(n-1); \\ Michel Marcus, Jun 08 2014

Formula

Equals A008864 INTERSECT A033993. - R. J. Mathar, Feb 20 2008

Extensions

Edited by R. J. Mathar, Feb 20 2008