# 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```
References: https://en.wikipedia.org/wiki/Centered_triangular_number

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