A187060 Primes p such that the polynomial x^2 + x + p generates only primes for x = 1..7.
11, 17, 41, 21557, 26681, 128981, 844427, 2073347, 3992201, 4889237, 6184637, 11900501, 21456047, 24598361, 33771581, 34864211, 50943791, 51448361, 51867197, 55793951, 56421347, 61218251, 67787537, 69726647, 76345121
Offset: 1
Keywords
Examples
a(4) <> 21577 because 0^2 + 0 + 21577 = 21577; 1^2 + 1 + 21577 = 21579 = 3 * 7193 thus exposing an error in Weber's paper; 2^2 + 2 + 21577 = 21583 = 113 * 191; 3^2 + 3 + 21577 = 21589 is prime; 4^2 + 4 + 21577 = 21597 = 3 * 23 * 313; 5^2 + 5 + 21577 = 21607 = 17 * 31 * 41 (a "3-brilliant number" rather than a prime); 6^2 + 6 + 21577 = 21619 = 13 * 1663; 7^2 + 7 + 21577 = 21633 = 3 * 7211.
Links
- Zak Seidov and Charles R Greathouse IV, Table of n, a(n) for n = 1..10000 (Zak Seidov found the first 400 terms)
- H. J. Weber, Regularities of Twin, Triplet and Multiplet Prime Numbers, arXiv:1103.0447 [math.NT], 2011-2012.
Programs
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Mathematica
okQ[n_] := And @@ PrimeQ[Table[i^2 + i + n, {i, 0, 7}]]; Select[Range[10000], okQ] (* T. D. Noe, Mar 03 2011 *)
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PARI
for(k=1,50000,p=prime(k); if(isprime(p+2) && isprime(p+6) && isprime(p+12) && isprime(p+20) && isprime(p+30) && isprime(p+42) && isprime(p+56),print(p),)) \\ Nathaniel Johnston, Apr 26 2011
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PARI
p=2;q=3;forprime(r=5,1e6,if(r-p==6 && q-p==2 && isprime(p+12) && isprime(p+20) && isprime(p+30) && isprime(p+42) && isprime(p+56),print(p));p=q;q=r) \\ Charles R Greathouse IV, Mar 04 2012
Extensions
a(12)-a(25) from Nathaniel Johnston, Apr 26 2011
Comments