A103746 Numbers n such that prime(n)*prime(n+1) - 1 is semiprime.

2, 3, 5, 10, 13, 20, 33, 60, 89, 109, 116, 138, 144, 152, 182, 189, 212, 223, 253, 258, 297, 320, 336, 350, 353, 375, 390, 418, 422, 487, 492, 498, 501, 549, 567, 579, 592, 616, 654, 671, 704, 755, 799, 800, 812, 826, 874, 893, 917, 921, 948, 951, 957, 967

Offset: 1

Author

Klaus Brockhaus, Mar 29 2005

Keywords

• nonn
• easy

Examples

			prime(10)*prime(11) - 1 = 29*31 - 1 = 898 = 2*449, hence 10 is a term.
		

Links

• Ray Chandler, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A001358, A006881, A103533.

Programs

PARI

for(n=1,1000,if(bigomega(prime(n)*prime(n+1)-1)==2,print1(n,",")))