A113519 Semiprimes in A056105.

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

Author

Jonathan Vos Post, Jan 12 2006

Keywords

• easy
• nonn

Comments

Intersection of A056105 and A001358.

Examples

			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.
		

Links

• Michael De Vlieger, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A001358, A056105.

Cf. A113524, A113525, A113527, A113528, A113530.

Programs

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 *)