This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A289555 #17 Jul 02 2025 19:23:53 %S A289555 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,25,26,27, %T A289555 28,29,30,31,33,34,35,37,38,39,41,42,43,44,45,46,47,49,50,51,52,53,55, %U A289555 57,58,59,61,62,63,65,66,67,68,69,70,71,73,74,75,76,77 %N A289555 Numbers that are not the product of two distinct composite numbers (A002808). %e A289555 Number 24 is not in the sequence because 24 = 4 * 6. %o A289555 (Magma) [n: n in [1..1000] | (#PrimeDivisors(n) eq 1 and NumberOfDivisors(n) lt 6) or (#PrimeDivisors(n) eq 2 and NumberOfDivisors(n) lt 8) or (#PrimeDivisors(n) ge 3 and NumberOfDivisors(n) lt 12) ]; %Y A289555 Complement of A289554. %Y A289555 Cf. A246716 (with two distinct primes), A008578 (with two distinct nonprimes), A289553 (with two distinct noncomposites). %K A289555 nonn %O A289555 1,2 %A A289555 _Jaroslav Krizek_, Jul 07 2017