A109288 Semiprimes equal to p*q + 1, where p and q are distinct primes.

15, 22, 34, 35, 39, 58, 86, 87, 94, 95, 119, 123, 134, 142, 143, 146, 159, 178, 202, 203, 206, 214, 215, 218, 219, 254, 299, 302, 303, 327, 335, 382, 394, 395, 446, 447, 454, 482, 502, 515, 527, 538, 543, 554, 566, 623, 634, 635, 695, 698, 699, 707, 718, 746

Offset

1,1

Links

Table of n, a(n) for n=1..54.

Mathematica

With[{nn=60}, Take[Select[Union[Times@@#+1&/@Subsets[Prime[Range[2nn]], {2}]], PrimeOmega[#]==2&], nn]] (* Harvey P. Dale, Apr 28 2018 *)

Prog

(PARI) for(i=1, 1000, if(bigomega(i)==2&&bigomega(i+1)==2&&issquare(i)==0, print1(i+1, ", "))) (Klasen)

Crossrefs

Cf. A109287, A109289, A109290.

Sequence in context: A038753 A006615 A114867 * A018889 A186525 A236107

Adjacent sequences: A109285 A109286 A109287 * A109289 A109290 A109291

Keyword

nonn

Author

Giovanni Teofilatto, Aug 20 2005

Extensions

More terms from Lambert Klasen (lambert.klasen(AT)gmx.net), Aug 21 2005

Status

approved