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 A172972 #4 Jun 02 2025 02:40:39 %S A172972 -1,-1,-1,-1,-3,-1,-1,-1,-1,-1,-1,0,2,0,-1,-1,-1,2,2,-1,-1,-1,-1,1,2, %T A172972 1,-1,-1,-1,-1,1,1,1,1,-1,-1,-1,-1,1,1,0,1,1,-1,-1,-1,-1,1,1,0,0,1,1, %U A172972 -1,-1,-1,-1,1,1,0,0,0,1,1,-1,-1 %N A172972 Subtraction triangle based on A029826: c(n)=Product[A029826(i),{i,0,n)];t(n,m)=c(n)-c(m)-c(n-m). %C A172972 Row sums are: %C A172972 {-1, -2, -5, -4, 0, 0, 0, 0, 0, 0, 0,...}. %F A172972 c(n)=Product[A029826(i),{i,0,n)]; %F A172972 t(n,m)=c(n)-c(m)-c(n-m) %e A172972 {-1}, %e A172972 {-1, -1}, %e A172972 {-1, -3, -1}, %e A172972 {-1, -1, -1, -1}, %e A172972 {-1, 0, 2, 0, -1}, %e A172972 {-1, -1, 2, 2, -1, -1}, %e A172972 {-1, -1, 1, 2, 1, -1, -1}, %e A172972 {-1, -1, 1, 1, 1, 1, -1, -1}, %e A172972 {-1, -1, 1, 1, 0, 1, 1, -1, -1}, %e A172972 {-1, -1, 1, 1, 0, 0, 1, 1, -1, -1}, %e A172972 {-1, -1, 1, 1, 0, 0, 0, 1, 1, -1, -1} %t A172972 (*A029826 Inverse of Salem polynomial : 1/(x^10 + x^9 - x^7 - x^6 - x^5 - x^4 - x^3 + x + 1).*) %t A172972 p[x_] = (x^(10) + x^9 - x^7 - x^6 - x^5 - x^4 - x^3 + x + 1); q[ x_] = Expand[x^10*p[1/x]]; a = Table[SeriesCoefficient[Series[1/ q[x], {x, 0, 100}], n], {n, 0, 100}]; %t A172972 c[n_] := Product[a[[m]], {m, 1, n}]; %t A172972 t[n_, m_] := c[n] - (c[m] + c[n - m]); %t A172972 Table[Table[t[n, m], {m, 0, n}], {n, 0, 10}]; %t A172972 Flatten[%] %Y A172972 A029826 %K A172972 sign,tabl,uned %O A172972 0,5 %A A172972 _Roger L. Bagula_, Feb 06 2010