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A241764
Semiprimes sp such that sp-3 is also semiprime.
2
9, 25, 38, 49, 58, 65, 77, 85, 94, 118, 121, 122, 145, 146, 158, 161, 169, 205, 206, 209, 217, 218, 221, 262, 265, 298, 301, 302, 305, 326, 329, 358, 361, 365, 394, 398, 454, 469, 481, 485, 505, 514, 517, 529, 538, 545, 554, 562, 565, 586, 589, 614
OFFSET
1,1
COMMENTS
Also semiprimes of the form 2^x - x.
The primes of the form 2^x - x are in A081296.
LINKS
EXAMPLE
a(3)= 38 = 2*19, which is semiprime: 38-3 = 35 = 5*7 is also semiprime.
a(5)= 58 = 2*29, which is semiprime: 58-3 = 55 = 5*11 is also semiprime.
MAPLE
with(numtheory): A241764:= proc(); if bigomega(x)=2 and bigomega(x-3)=2 then RETURN (x); fi; end: seq(A241764 (), x=1..2000);
MATHEMATICA
Flatten[Position[Partition[Table[If[PrimeOmega[n]==2, 1, 0], {n, 700}], 4, 1], _?(First[ #] ==Last[#]==1&), {1}, Heads->False]]+3 (* Harvey P. Dale, Dec 21 2015 *)
PROG
(PARI) for(k=1, 500, if(bigomega(k)==2 && bigomega(k-3)==2, print1(k, ", "))) \\ Colin Barker, May 07 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
K. D. Bajpai, Apr 29 2014
STATUS
approved