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1.0 KiB
id | title | challengeType | forumTopicId | dashedName |
---|---|---|---|---|
5900f3f21000cf542c50ff04 | Problem 133: Repunit nonfactors | 5 | 301761 | problem-133-repunit-nonfactors |
--description--
A number consisting entirely of ones is called a repunit. We shall define R(k)
to be a repunit of length k
; for example, R(6) = 111111
.
Let us consider repunits of the form R({10}^n)
.
Although R(10)
, R(100)
, or R(1000)
are not divisible by 17, R(10000)
is divisible by 17. Yet there is no value of n for which R({10}^n)
will divide by 19. Remarkably, 11, 17, 41, and 73 are the only four primes below one-hundred that can be a factor of R({10}^n)
.
Find the sum of all the primes below one-hundred thousand that will never be a factor of R({10}^n)
.
--hints--
repunitNonfactors()
should return 453647705
.
assert.strictEqual(repunitNonfactors(), 453647705);
--seed--
--seed-contents--
function repunitNonfactors() {
return true;
}
repunitNonfactors();
--solutions--
// solution required