A254002 Numbers n such that 1 + 46* Sum_{k=1..n} 100^(k-1) is prime.
1, 3, 4, 6, 9, 45, 57, 130, 142, 198, 273, 331, 2494, 8437, 10210, 17377, 19972
Offset: 1
Examples
47 is prime, so 1 is in the sequence. 4647 is not prime, so 2 is not in the sequence. 464647 is prime, so 3 is in the sequence. 46464647 is prime, so 4 is in the sequence.
Links
- Dario A. Alpern, Factorization using the Elliptic Curve Method.
Crossrefs
Cf. A110705.
Programs
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PARI
isok(n) = isprime(1 + 46*sum(k=1, n, 100^(k-1))); \\ Michel Marcus, Jan 22 2015
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PARI
is(n)=ispseudoprime(46*(100^n-1)/99+1) \\ Charles R Greathouse IV, Jan 22 2015
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PFGW
ABC2 46*(100^$a-1)/99+1 a: from 1 to 10000 Charles R Greathouse IV, Jan 22 2015
Extensions
a(13)-a(14) from Charles R Greathouse IV, Jan 22 2015
a(15) from Charles R Greathouse IV, Jan 23 2015
a(16)-a(17) from Charles R Greathouse IV, Jan 26 2015
Comments