# Centered triangular number in PL/SQL

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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