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 A386949 #8 Aug 11 2025 10:32:45 %S A386949 1,1,2,2,1,3,3,3,3,1,2,2,4,4,1,5,5,5,5,5,5,1,2,2,3,3,6,6,6,6,1,7,7,7, %T A386949 7,7,7,7,7,1,2,2,4,4,4,4,4,4,8,8,8,8,1,3,3,3,3,9,9,9,9,9,9,9,9,1,2,2, %U A386949 5,5,5,5,10,10,10,10,10,10,1,11,11,11,11,11,11,11,11,11,11 %N A386949 Irregular triangle whose n-th row lists the nonzero terms of the n-th column of A386755. %e A386949 Triangle begins: %e A386949 1; %e A386949 1, 2, 2; %e A386949 1, 3, 3, 3, 3; %e A386949 1, 2, 2, 4, 4; %e A386949 1, 5, 5, 5, 5, 5, 5; %e A386949 1, 2, 2, 3, 3, 6, 6, 6, 6; %e A386949 1, 7, 7, 7, 7, 7, 7, 7, 7; %e A386949 1, 2, 2, 4, 4, 4, 4, 4, 4, 8, 8, 8, 8; %e A386949 1, 3, 3, 3, 3, 9, 9, 9, 9, 9, 9, 9, 9; %e A386949 1, 2, 2, 5, 5, 5, 5, 10, 10, 10, 10, 10, 10; %e A386949 ... %o A386949 (PARI) orow(n) = my(v=vector(n), m=n); for(k=1, n, my(keepm = m); while(m%k, m--); if (m == 0, keepm=m, v[m] = k; m--); ); v; \\ A386755 %o A386949 nrow(n) = my(ok=1, k=1, last=-1, list=List(), r); while(ok, r=row(k); if ((#r >= n) && r[n], listput(list, r[n])); k++; if (#r>=n, if ((last==n) && (r[n]==0), ok = 0, last = r[n]))); Vec(list); %Y A386949 Cf. A386755 (original triangle), A386520 (row sums). %Y A386949 Cf. A027750. %K A386949 nonn,tabf %O A386949 1,3 %A A386949 _Michel Marcus_, Aug 10 2025