(y -1)/2=a

If a is odd, b = (a-1) / 2, if a is even b = (a +y-1) / 2

If b is odd, c = (b-1) / 2, if b is even c = (a +y-1) / 2

If y is divisible by 7, c will be divisible by 7..........

Works for any Mersenne Number....

Works because whatever I do to y to get to zero I have to be able to do to a multiple of y, to get to a remainder zero for y! And 7-1/2=3 3-1/2=1 1-1/2=0.

Example:35= 5*7,

35-1/2=17, 17-1/2=8 (8+35-1)/2=21,

21= 3*7

Example: 27=3*9

27-1/2=13 13-1/2=6

6=3*2

3-1/2=1

1-1/2=0

ganesh wrote:Monox D. I-Fly wrote:Who is jane?

JaneFairfax is a member with close to 7000 posts! I personally feel the member in question is smart!

Oh, a deleted post, then?

The individual continues to be a member.

]]>Monox D. I-Fly wrote:kylekatarn wrote:you are really angry today jane...what's wrong?

yelling in several postsWho is jane?

JaneFairfax is a member with close to 7000 posts! I personally feel the member in question is smart!

Oh, a deleted post, then?

]]>kylekatarn wrote:you are really angry today jane...what's wrong?

yelling in several postsWho is jane?

JaneFairfax is a member with close to 7000 posts! I personally feel the member in question is smart!

]]>you are really angry today jane...what's wrong?

yelling in several posts

Who is jane?

]]>(Please don't yell)

]]>Divide the number into groups of 3 (starting from Right) and find the difference between the sum of the numbers in odd and even places.. If the difference is '0' or a multiple of 7 or 13 (as the case may be), its divisible by it!

e.g. 4537764

==> 4 537 764

==> (764+4) - (537)

==> 231= 7*33 ! Hence divisible!