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 A174843 #8 May 02 2025 03:16:42
%S A174843 1,1,2,1,2,4,1,2,3,6,1,2,5,10,1,2,3,4,6,12,1,2,4,8,16,1,2,3,6,9,18,1,
%T A174843 2,11,22,1,2,4,7,14,28,1,2,3,5,6,10,15,30,1,2,3,4,6,9,12,18,36,1,2,4,
%U A174843 5,8,10,20,40,1,2,3,6,7,14,21,42,1,2,23,46,1,2,4,13,26,52,1,2,29,58,1,2,3,4
%N A174843 Irregular triangle in which row n lists the divisors of prime(n)-1.
%C A174843 Row n begins with 1, ends with prime(n)-1, and has A008328(n) terms.
%H A174843 T. D. Noe, <a href="/A174843/b174843.txt">Rows n=1..500 of triangle, flattened</a>
%e A174843 The first 10 rows:
%e A174843 1
%e A174843 1, 2
%e A174843 1, 2, 4
%e A174843 1, 2, 3, 6
%e A174843 1, 2, 5, 10
%e A174843 1, 2, 3, 4, 6, 12
%e A174843 1, 2, 4, 8, 16
%e A174843 1, 2, 3, 6, 9, 18
%e A174843 1, 2, 11, 22
%e A174843 1, 2, 4, 7, 14, 28
%t A174843 Flatten[Table[Divisors[p-1], {p, Prime[Range[100]]}]]
%o A174843 (PARI) row(n) = divisors(prime(n)-1); \\ _Amiram Eldar_, May 02 2025
%Y A174843 Cf. A008328 (row lengths), A008332 (row sums).
%K A174843 nonn,tabf
%O A174843 1,3
%A A174843 _T. D. Noe_, Mar 30 2010