Talk:Descartes number

Negative primes
Either the definition needs a modification, or there is another Descartes number. If we pretend that -127 is a positive prime, i.e., $$\sigma(-127)=-126$$, then


 * $$\sigma(3^47^211^219^2(-127)) = \sigma(3^4)\sigma(7^2)\sigma(11^2)\sigma(19^2)\sigma(-127) = (11^2)\cdot(3\cdot19)\cdot(7\cdot19)\cdot(3\cdot127)\cdot(-2\cdot3^2\cdot7) = 2\cdot3^47^211^219^2(-127).$$ — Preceding unsigned comment added by 84.55.98.173 (talk) 07:27, 27 January 2016 (UTC)