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 A227396 #23 Oct 05 2013 04:44:44 %S A227396 1,-1,2,-2,3,3,-3,4,6,4,-4,5,10,10,5,-5,6,15,20,15,6,-6,7,21,35,35,21, %T A227396 7,-7,8,28,56,70,56,28,8,-8,9,36,84,126,126,84,36,9,-9,10,45,120,210, %U A227396 252,210,120,45,10,-10 %N A227396 Triangle A074909(n) with the first column equal to 1 followed by -A000027(n) instead of A000012. %C A227396 Triangle leading to A164555(n)/A027642(n). %C A227396 Starting from B(0)=1, the Bernoulli numbers B(n) with B(1)=1/2 are such that %C A227396 1*B(0) = 1 %C A227396 -1*B(0) +2*B(1)= 0 --> B(1)=1/2 %C A227396 -2*B(0) +3*B(1) +3*B(2) = 0 --> B(2)=1/6 %C A227396 -3*B(0) +4*B(1) +6*B(2) +4*B(3) = 0 --> B(3)=0 %C A227396 -4*B(0) +5*B(1) +10*B(2) +10*B(3) +5*B(4) = 0 --> B(4)=-1/30 etc. %C A227396 Row sum of A: A130103(n+1). %C A227396 Row sum's absolute values of A: A145071(n). %F A227396 T(n,k) = A074909(n,k) for n>0 and k>0, T(0,0)=1, T(n,0)=-n for n>0. %e A227396 a(n) triangle is A: %e A227396 1 %e A227396 -1 2 %e A227396 -2 3 3 %e A227396 -3 4 6 4 %e A227396 -4 5 10 10 5 %e A227396 -5 6 15 20 15 6 %e A227396 -6 7 21 35 35 21 7 etc. %K A227396 sign,tabl %O A227396 0,3 %A A227396 _Paul Curtz_, Sep 20 2013