A289554 - OEIS

%I #18 Jul 02 2025 19:24:03

%S 24,32,36,40,48,54,56,60,64,72,80,84,88,90,96,100,104,108,112,120,126,

%T 128,132,135,136,140,144,150,152,156,160,162,168,176,180,184,189,192,

%U 196,198,200,204,208,210,216,220,224,225,228,232,234,240,243,248,250

%N Numbers that are the product of two distinct composite numbers (A002808).

%e Number 24 is in the sequence because 24 = 4 * 6.

%o (Magma) [n: n in [1..1000] | (#PrimeDivisors(n) eq 1 and NumberOfDivisors(n) ge 6) or (#PrimeDivisors(n) eq 2 and NumberOfDivisors(n) ge 8) or (#PrimeDivisors(n) ge 3 and NumberOfDivisors(n) ge 12) or (#PrimeDivisors(n) ge 4)];

%Y Complement of A289555.

%Y Cf. A006881 (with two distinct primes), A002808 (with two distinct nonprimes), A167171 (with two distinct noncomposites).

%K nonn

%O 1,1

%A _Jaroslav Krizek_, Jul 07 2017