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Centred Triangular Prime Days
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A centred triangular prime is a centred triangular number that is prime.

Centred triangular numbers are of the form (3n2 + 3n + 2) / 2

A centred triangular number is a centred figurate number that represents a triangle with a dot in the centre and all other dots surrounding the centre in successive triangular layers.

The figures for the first four centred triangular numbers are shown below: