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

1,1

Links

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

Example

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

Prog

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

Crossrefs

Cf. A001358, A006881, A103533.

Sequence in context: A162404 A084760 A186082 * A071848 A268176 A120938

Adjacent sequences: A103743 A103744 A103745 * A103747 A103748 A103749

Keyword

nonn,easy

Author

Klaus Brockhaus, Mar 29 2005

Status

approved