OFFSET
1,1
COMMENTS
Odd semiprimes sp(k) = A001358(k) such that sp(k-1) and sp(k+1) are even. Values of k: 3, 9, 11, 13, 15, 26, 28, 34, 46, 51, 63, 83, 112, 114, 125, 148, 175, 177, 190, 230, 242, 253, 259, 264, 278, 280, 293.
EXAMPLE
MATHEMATICA
s = Select[Range[2300], Plus @@ Last /@ FactorInteger[#] == 2 &]; Transpose[ Select[ Partition[s, 3, 1], Mod[#, 2] == {0, 1, 0} &]][[2]] (* Giovanni Resta, Jun 10 2018 *)
Module[{nn=2500, sp}, sp=Select[Range[nn], PrimeOmega[#]==2&]; Select[Partition[ sp, 3, 1], Mod[ #, 2] =={0, 1, 0}&]][[;; , 2]] (* Harvey P. Dale, Mar 03 2023 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Zak Seidov, Jun 10 2018
STATUS
approved