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A113519
Semiprimes in A056105.
10
9, 22, 134, 177, 226, 482, 737, 1046, 1282, 1681, 1977, 2641, 3202, 3401, 3817, 4034, 4486, 5462, 5721, 6817, 7401, 7702, 8966, 9634, 9977, 10681, 11042, 11409, 12937, 15409, 16726, 17177, 18566, 21506, 28617, 29801
OFFSET
1,1
COMMENTS
Intersection of A056105 and A001358.
LINKS
EXAMPLE
A056105(44) = 3*44^2 - 2*44 + 1 = 5721 = 3 * 1907 which is a semiprime.
A056105(24) = 3*24^2 - 2*24 + 1 = 1681 = 41^2 which is a semiprime (the two prime factors need not be distinct).
A056105(100) = 3*100^2 - 2*100 + 1 = 29801 = 17 * 1753, which is a semiprime.
MAPLE
for n from 0 to 300 do
s := 3*n^2-2*n+1 ;
if isA001358(s) then
printf("%d, ", s) ;
end if;
end do: # R. J. Mathar, Jun 30 2020
MATHEMATICA
Select[Array[3 #^2 - 2 # + 1 &, 100], PrimeOmega[#] == 2 &] (* Michael De Vlieger, Mar 17 2021 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Jonathan Vos Post, Jan 12 2006
STATUS
approved