## The first thirteen palindromic triangular numbers

Here are the first thirteen palindromic triangular numbers:

$T_0 \; = \; 0$
$T_1 \; = \; 1$
$T_2 \; = \; 3$
$T_3 \; = \; 6$
$T_{10} \; = \; 55$
$T_{11} \; = \; 66$
$T_{18} \; = \; 171$
$T_{34} \; = \; 595$
$T_{36} \; = \; 666$
$T_{77} \; = \; 3003$
$T_{109} \; = \; 5995$
$T_{132} \; = \; 8778$
$T_{173} \; = \; 15051$

The sum of the indices is itself palindromic:

$0+1+2+3+10+11+18+34+36+77+109+132+173=606$

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## About benvitalis

math grad - Interest: Number theory
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### 2 Responses to The first thirteen palindromic triangular numbers

1. paul says:

You could have also gone 1 more to T363 = 66066
and 606 + 363 = 969.
P.