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 A130471 #3 Sep 08 2022 08:45:30 %S A130471 0,2,5,21,106,640,4527,36539,331508,3338358,36946489,445724977, %T A130471 5821580670,81839381996,1232102291651,19778348559015,337223021210632, %U A130471 6086161135368034,115915940643233613,2323409451689985053 %N A130471 First differences of antidiagonal sums of triangular array T: T(j,k) = k*(j-k)! for k < j, T(j,k) = 1 for k = j; 1 <= k <= j. %C A130471 a(n) = A130470(n+1) - A130470(n). %e A130471 a(7) = A130470(8) - A130470(7) = 5302 - 775 = 4527. %o A130471 (Magma) m:=21; T:=[ [ k*Factorial(j-k): k in [1..j-1] ] cat [ 1 ]: j in [1..m] ]; S:=[ &+[ T[j-k+1][k]: k in [1..(j+1) div 2] ]: j in [1..m] ]; [ S[j+1]-S[j]: j in [1..m-1] ]; %Y A130471 Cf. A130469 (T read by rows), A129867 (row sums), A130470 (antidiagonal sums). %K A130471 nonn %O A130471 1,2 %A A130471 _Klaus Brockhaus_, May 28 2007