A146560 Squarefree semiprimes n such that n+1 is squarefree and n+2 is prime.

21, 57, 65, 69, 77, 129, 177, 209, 221, 237, 309, 329, 365, 381, 417, 437, 497, 501, 545, 597, 681, 689, 717, 785, 905, 965, 1037, 1101, 1121, 1257, 1317, 1397, 1437, 1497, 1509, 1541, 1569, 1577, 1661, 1757, 1821, 1829, 1865, 1929, 1977, 1985, 2201, 2369, 2577, 2589, 2669, 2705, 2885, 2901

Offset: 1

Author

Giovanni Teofilatto, Nov 01 2008

Keywords

• easy
• nonn

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A077064, A146319.

Programs

Mathematica

Select[Range[3000],PrimeOmega[#]==2&&SquareFreeQ[#]&&SquareFreeQ[#+1]&&PrimeQ[#+2]&] (* Harvey P. Dale, Jan 20 2020 *)

Formula

(A006881 INTERSECT A040976) INTERSECT A005117

Extensions

Definition corrected and more terms supplied by R. J. Mathar, Nov 02 2008