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

%I #8 Jan 20 2020 20:36:42

%S 21,57,65,69,77,129,177,209,221,237,309,329,365,381,417,437,497,501,

%T 545,597,681,689,717,785,905,965,1037,1101,1121,1257,1317,1397,1437,

%U 1497,1509,1541,1569,1577,1661,1757,1821,1829,1865,1929,1977,1985,2201,2369,2577,2589,2669,2705,2885,2901

%N Squarefree semiprimes n such that n+1 is squarefree and n+2 is prime

%H Harvey P. Dale, <a href="/A146560/b146560.txt">Table of n, a(n) for n = 1..1000</a>

%F (A006881 INTERSECT A040976) INTERSECT A005117

%t Select[Range[3000],PrimeOmega[#]==2&&SquareFreeQ[#]&&SquareFreeQ[#+1]&&PrimeQ[#+2]&] (* _Harvey P. Dale_, Jan 20 2020 *)

%Y Cf. A077064, A146319.

%K easy,nonn

%O 1,1

%A _Giovanni Teofilatto_, Nov 01 2008

%E Definition corrected and more terms supplied by _R. J. Mathar_, Nov 02 2008