Function gcd

test/compute-engine/arithmetic.test.ts:1864–1865

(...ops: ReturnType<typeof ce.parse>[])

    expect(
      ce.parse('\\prod_{n=1}^{b}(n+1)').simplify().toString()
    ).toMatchInlineSnapshot(`(b + 1)! / 1!`);
  });

  it('should evaluate product with index shift (n+1)', () => {
    // 2*3*4*5 = 120