👉 In mathematics, a subtriangular number is a positive integer that can be expressed as the sum of two triangular numbers. These numbers are also called triangular subtrahends or triangular subtriangular numbers. For example: - 2 is a subtriangular number because it equals the sum of two triangular numbers: 2 = 1 + 1. - 3 is not a subtriangular number, as it does not equal the sum of two triangular numbers. Subtriangularity
