Question

Can someone really skilled in number theory help out? I am not talking about a school homework, i am trying to solve a problem for fun. Also if you can give links I will just read. I googled but couldn't find anything interesting.

Answer 1

if a,b,c are prime numbers
and a^2-b^2=c
find a,b,c

Answer 2

I guess 3, 2 and 5 are prime numbers? This is just by trial and error though :)

Answer 3

ok good but it has a solution
look
(a+b)(a-b) =c*1
all of theme are prime
so a+b=c
and a-b=1
because a-b <a+b (in N)
just two prime number can be a,b
because a=b+1
only 2 is even prime number
but all the others ore odd numbers
so a=3 ,b=2
hence c=2+3

Answer 4

i am talking about a completely different stuff here ppl. Have you heard of the sigma function? Sum of the divisors of a number?

Answer 5

please don't post random stuff here

Answer 6

No, not familiar with that, sorry.

Answer 7

now try other problem
how many prime number like "p" exist such that
5p+1 is sqr of natural number

Answer 8

how many prime in sequence of a(n)=n!+3

Answer 9

I can't see an original question by you mivanov.

Answer 10

It goes like example for 12
we have divisors
1,2,3,4,6,12
and we use sigma2
which is the sum of these squared
1^2+2^2+3^2+4^2+6^2+12^2.
so we call that sigma2
and then we want to calculate sum of sigma2 for n ranging from 1 to 10^15 and modulo 10^9 the result

Answer 11

it's this problem. i made a program that calculates it to like 1 000 000
https://projecteuler.net/problem=401
but it's just slow for numbers above 1 000 000

Answer 12

amoodarya can you help me with problem? give me some hints about the SIGMA2 function please

Answer 13

@amoodarya

Answer 14

can you list 10^15 divisors ?
if yes
from 2^4 *5^4 sima2 func modulo 10^9 is zero
so you have to compute 1^2+2^2 +5^2 +10^2 +..10^4 mod 10^9

Answer 15

do you know the formula that give sum of divisors?