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

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Output:

19
235