Thread: theory on Mersenne primes ? View Single Post
2010-11-12, 20:41   #49
axn

Jun 2003

469910 Posts

Quote:
 Originally Posted by science_man_88 Code:  (11:39) gp > sumdigits(47)*sumdigits(178481) %69 = 4 (16:19) gp > sumdigits(47*178481) %70 = 4 in this case it works without the outer sumdigits in the first expression because both sumdigits are below 5 so it can't add up above 9.
See the highlighted part. That is the correct relation. This follows from the fact that sumdigits(x) is equivalent to x%9.