Search: id:A071576 Results 1-1 of 1 results found. %I A071576 %S A071576 1,1,1,165,5415,12705,256410,256410,6480303060,217245863835, %T A071576 946622690475,35511547806735,439116128090640 %N A071576 a(n) = least k such that 2ik+1 is prime for all 1<=i<=n. %t A071576 k = 1; Do[ While[p = Table[2*i*k + 1, {i, 1, n}]; Union[ PrimeQ[p]] != {True}, k++ ]; Print[k], {n, 1, 15}] (Robert G. Wilson v) %o A071576 (PARI) for(n=1,6,s=1; while(sum(i=1,n,isprime(2*s*i+1))