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 A185018 #16 Jun 28 2024 04:22:31
%S A185018 1,-2,1,1,-2,1,0,1,-2,1,0,0,1,-2,1,0,0,0,1,-2,1,0,0,0,0,1,-2,1,0,0,0,
%T A185018 0,0,1,-2,1,0,0,0,0,0,0,1,-2,1,0,0,0,0,0,0,0,1,-2,1,0,0,0,0,0,0,0,0,1,
%U A185018 -2,1,0,0,0,0,0,0,0,0,0,1,-2,1,0,0,0,0,0,0,0,0,0,0,1,-2,1
%N A185018 Inverse to sequence matrix for natural numbers.
%C A185018 Riordan array ((1-x)^2,x). Inverse matrix is Riordan array (1/(1-x)^2,x), A004736. Row sums are (1,-1,0,0,0,0,0,0,0,0,0,...). Diagonal sums are (1,-2,2,-2,2,-2,2,-2,2,-2,2,...).
%F A185018 T(n,n)=1, T(n,n-1)=-2, T(n,n-2)=1, T(n,k)=0 where k<n-2.
%e A185018 Triangle begins :
%e A185018 1 ;
%e A185018 -2, 1 ;
%e A185018 1, -2, 1 ;
%e A185018 0, 1, -2, 1 ;
%e A185018 0, 0, 1, -2, 1 ;
%e A185018 0, 0, 0, 1, -2, 1 ;
%e A185018 0, 0, 0, 0, 1, -2, 1 ;
%e A185018 0, 0, 0, 0, 0, 1, -2, 1 ;
%e A185018 0, 0, 0, 0, 0, 0, 1, -2, 1 ;
%t A185018 Array[PadLeft[{1, -2, 1}, #] &, 15] (* _Paolo Xausa_, Jun 27 2024 *)
%Y A185018 Cf. A004736, A167194 (unsigned version).
%K A185018 easy,sign,tabl
%O A185018 0,2
%A A185018 _Philippe Deléham_, Oct 12 2011