Euler's Pentagonal Numbers Theorem/Corollary 1/Examples/12

Example of Euler's Pentagonal Numbers Theorem: Corollary 1

 * $\map {\sigma_1} {12} = \map {\sigma_1} {11} + \map {\sigma_1} {10} - \map {\sigma_1} 7 - \map {\sigma_1} 5 + 12$