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 A173662 #17 Jun 28 2024 21:10:37
%S A173662 0,2,0,1,3,0,2,4,1,0,2,2,5,4,0,3,3,6,5,1,0,1,3,3,1,7,6,0,2,4,4,2,8,7,
%T A173662 1,0,1,1,7,5,11,10,4,3,0,2,2,8,6,12,11,5,4,1,0,1,3,6,3,5,3,12,11,8,7,
%U A173662 0,2,4,7,4
%N A173662 Triangle read by rows: T(n,k) = semiprime(n) mod semiprime(k), 1 <= k <= n.
%C A173662 Row sums are 0, 2, 4, 7, 13, 18, 28, ...
%e A173662 Triangle begins:
%e A173662 0,
%e A173662 2,0;
%e A173662 1,3,0;
%e A173662 2,4,1,0;
%e A173662 2,2,5,4,0;
%e A173662 3,3,6,5,1,0;
%e A173662 1,3,3,1,7,6,0;
%e A173662 2,4,4,2,8,7,1,0;
%t A173662 SemiprimeQ[n_Integer] := If[Abs[n]<2, False, (2==Plus@@Transpose[FactorInteger[Abs[n]]][[2]])]; sp = Select[Range[100], SemiprimeQ]; Flatten[Table[Mod[sp[[n]], sp[[Range[n]]]], {n,Length[sp]}]]
%Y A173662 Cf. A001358, A173655.
%K A173662 nonn,tabl,easy
%O A173662 1,2
%A A173662 _Juri-Stepan Gerasimov_, Nov 28 2010
%E A173662 46th term corrected by _D. S. McNeil_, Nov 24 2010