%I #8 Feb 08 2022 19:15:33
%S 1,3,1,6,1,2,10,1,2,3,15,1,2,3,4,21,1,2,3,4,5,28,1,2,3,4,5,6,36,1,2,3,
%T 4,5,6,7,45,1,2,3,4,5,6,7,8
%N Triangle read by rows, T(n) followed by 1, 2, 3, ..., n-1.
%C Row sums = n^2.
%H Harvey P. Dale, <a href="/A130270/b130270.txt">Table of n, a(n) for n = 1..1000</a>
%F Triangle read by rows, T(n) followed by 1,2,3,...,n-1. Row differences of triangle A130269 starting from the left.
%e First few rows of the triangle:
%e 1;
%e 3, 1;
%e 6, 1, 2;
%e 10, 1, 2, 3;
%e 15, 1, 2, 3, 4;
%e ...
%e Row 4 = (10, 1, 2, 3) = differences of row 4 of A130269: (10, 11, 13, 16).
%t Table[Join[{(n(n+1))/2,Range[n-1]}],{n,10}]//Flatten (* _Harvey P. Dale_, Dec 31 2021 *)
%Y Cf. A000217, A130269.
%K nonn,tabl
%O 1,2
%A _Gary W. Adamson_, May 18 2007