A289357 Least number k such that n^2 + n - k is prime.
0, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 5, 1, 11, 1, 1, 13, 5, 1, 1, 1, 3, 5, 1, 3, 1, 5, 1, 7, 1, 1, 5, 5, 3, 1, 5, 7, 1, 1, 3, 1, 5, 3, 1, 1, 1, 5, 1, 3, 1, 5, 3, 1, 1, 1, 1, 5, 9, 1, 1, 3, 17, 5, 1, 1, 1, 7, 1, 13, 1, 5, 19, 3, 19, 7, 1, 19, 11, 3, 7, 5, 3, 1, 11, 1
Offset: 1
Keywords
Links
- Robert Israel, Table of n, a(n) for n = 1..10000
Programs
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Maple
0, seq(n^2 + n - prevprime(n^2+n), n=2..100); # Robert Israel, Jul 03 2017
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Mathematica
Table[k = 0; While[! PrimeQ[n^2 + n - k], k++]; k, {n, 85}] (* Michael De Vlieger, Jul 04 2017 *) -
PARI
for(n=1,85,k={my(k=0);while(!isprime(n^2+n-k),k++);k;};print1(k", "))
Comments