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 A077553 #17 May 28 2025 20:58:21 %S A077553 4,4,6,4,6,9,4,6,9,10,4,6,9,10,15,4,6,9,10,15,25,4,6,9,10,14,15,21,4, %T A077553 6,9,10,14,15,21,25,4,6,9,10,14,15,21,25,35,4,6,9,10,14,15,21,25,35, %U A077553 49,4,6,9,10,14,15,21,22,25,33,35,4,6,9,10,14,15,21,22,25,33,35,49,4,6,9,10 %N A077553 Triangle in which the n-th row contains n distinct composite numbers with the least product and has least number of prime divisors. No member of a row is a multiple of another member of the row. %C A077553 If there are two sets of distinct composite numbers satisfying the above condition then the set with lesser product is chosen irrespective of the number of prime divisors. Perhaps the ambiguity may not arise. E.g., row 6 is 4,6,9,10,15,25. This row cannot be extended to get the next row without bringing in another prime because every number divisible by 2,3 or 5 will be a multiple of one of the previous terms. Hence in row 7, prime 7 has to be brought in and then we get a new set of numbers: 4,6,9,10,14,15,21. %H A077553 Sean A. Irvine, <a href="/A077553/b077553.txt">Table of n, a(n) for n = 1..5050</a> (rows 1..100 flattened) %e A077553 4; %e A077553 4,6; %e A077553 4,6,9; %e A077553 4,6,9,10; %e A077553 4,6,9,10,15; %e A077553 4,6,9,10,15,25; %e A077553 4,6,9,10,14,15,21; %Y A077553 Cf. A001358, A005843, A077554, A077555, A087112. %K A077553 nonn,tabl %O A077553 1,1 %A A077553 _Amarnath Murthy_, Nov 10 2002 %E A077553 More terms from _Ray Chandler_, Aug 21 2003 %E A077553 Offset corrected by _Sean A. Irvine_, May 28 2025