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Triangle read by rows, T(n) followed by 1, 2, 3, ..., n-1.
1

%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