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# Centered triangular number in PL/SQL

• Last Updated : 31 Oct, 2018

Prerequisite PL/SQL introduction
In PL/SQL code groups of commands are arranged within a block. A block group related declarations or statements. In declare part, we declare variables and between begin and end part, we perform the operations.

Given n and task is to find nth centered triangular number. A centered triangular number is a centered number that represents a triangle with a dot in the center and all other dots surrounding the center in successive triangular layers.
Examples:

```Input: n = 6
Output: 64

Input: n = 10
Output: 166
```

The first few centered triangular number series are:
1, 4, 10, 19, 31, 46, 64, 85, 109, 136, 166, 199, 235, 274, 316, 361, 409, 460………………………

Approach
nth Term of centered triangular number is given by:

``` ```

Below is the required implementation:

 `--PL/SQL Program to find the nth Centered triangular number ``-- declaration section ``DECLARE` `  ``x NUMBER; ``  ``n NUMBER; ``   ` `  ``--utility function ``  ``FUNCTION` `Centered_triangular_num(n ``IN` `NUMBER) ``    ``RETURN` `NUMBER ``  ``IS` `    ``z NUMBER; ``  ``BEGIN` `   ` `    ``--formula applying ``    ``z := (3 * n * n + 3 * n + 2) / 2; ``    ``RETURN` `z; ``  ``END``; ``   ` `  ``--driver code ``  ``BEGIN` `    ``n := 3; ``    ``x := centered_triangular_num(n); ``    ``dbms_output.Put_line(x); ``    ``n := 12; ``    ``x := centered_trigunal_num(n); ``    ``dbms_output.Put_line(x); ``  ``END``; ``  ``--End of program`

Output:

```19
235```
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