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 A104030 #10 Jun 13 2017 01:28:38 %S A104030 1,-2,1,7,-5,1,-41,32,-9,1,376,-299,91,-14,1,-5033,4015,-1241,205,-20, %T A104030 1,92821,-74080,22954,-3842,400,-27,1,-2257166,1801537,-558402,93652, %U A104030 -9863,707,-35,1,69981919,-55855829,17313721,-2904530,306409,-22190,1162,-44,1,-2694447797,2150565968 %N A104030 Matrix inverse, read by rows, of triangle A104029, which forms the pairwise sums of trinomial coefficients. %C A104030 Column 0 forms signed Hammersley's polynomial p_n(1) (A006846), offset 1. %C A104030 Row sums equal negative Genocchi numbers of first kind (A001469). %C A104030 Rows form polynomials R_n(x) such that: R_n(3) = 1 for n>=0 and R_n(1/2) = (-1)^n*A005647(n+1)/2^n (signed Salie numbers). %C A104030 Column 1 forms A104031. %C A104030 Unsigned row sums form A104032. %e A104030 Rows begin: %e A104030 1; %e A104030 -2,1; %e A104030 7,-5,1; %e A104030 -41,32,-9,1; %e A104030 376,-299,91,-14,1; %e A104030 -5033,4015,-1241,205,-20,1; %e A104030 92821,-74080,22954,-3842,400,-27,1; %e A104030 -2257166,1801537,-558402,93652,-9863,707,-35,1; ... %o A104030 (PARI) T(n,k)=if(n<k || k<0,0,((matrix(n+2,n+2,m,j,if(m>=j, polcoeff((1+x+x^2)^(m-1)+O(x^(2*j)),2*j-2)+ polcoeff((1+x+x^2)^(m-1)+O(x^(2*j)),2*j-1))))^-1)[n+1,k+1]) %Y A104030 Cf. A006846, A001469, A005647, A104027, A104029, A104031, A104032. %K A104030 sign,tabl %O A104030 0,2 %A A104030 _Paul D. Hanna_, Feb 26 2005