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 A181511 #15 Jan 27 2019 10:58:43 %S A181511 1,1,2,1,3,6,1,4,12,24,1,5,20,60,120,1,6,30,120,360,720,1,7,42,210, %T A181511 840,2520,5040,1,8,56,336,1680,6720,20160,40320,1,9,72,504,3024,15120, %U A181511 60480,181440,362880,1,10,90,720,5040,30240,151200,604800,1814400,3628800 %N A181511 Triangle T(n,k) = n!/(n-k)! read by rows, 0 <= k < n. %C A181511 Row n contains the same set of values as row A181512(n,.), which are related to labeled rooted trees (A000169) and Bell numbers (A000110) respectively. %H A181511 Reinhard Zumkeller, <a href="/A181511/b181511.txt">Rows n = 0..100 of triangle, flattened</a> %F A181511 T(n,k) = A008279(n,k). - _R. J. Mathar_, Mar 03 2011 %e A181511 The triangle begins: %e A181511 1; %e A181511 1, 2; %e A181511 1, 3, 6; %e A181511 1, 4, 12, 24; %e A181511 which is A181512 without duplicates. %p A181511 A181511 := proc(n,k) n!/(n-k)! ; end proc: %p A181511 seq(seq(A181511(n,k),k=0..n-1),n=1..16) ; # _R. J. Mathar_, Mar 03 2011 %o A181511 (Haskell) %o A181511 a181511 n k = a181511_tabl !! (n-1) !! k %o A181511 a181511_row n = a181511_tabl !! (n-1) %o A181511 a181511_tabl = tail $ map init a008279_tabl %o A181511 -- _Reinhard Zumkeller_, Nov 18 2012 %Y A181511 Cf. A002627 (row sums). %K A181511 nonn,tabl,easy %O A181511 1,3 %A A181511 _Alford Arnold_, Oct 26 2010