This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A231819 #8 Nov 18 2013 15:25:52
%S A231819 3,1,2,2,6,2,2,2,8,2,2,3,2,3,2,5,2,2,8,5,2,2,8,2,2,3,6,2,12,3,8,5,10,
%T A231819 2,6,2,12,2,2,3,2,2,2,3,2,2,18,3,2,2,8,2,20,3,6,2,18,3,2,3,12,2,2,2,6,
%U A231819 7,8,6,2,3,14,3,2,3,6,2,6,3,8,2,2,5,6,5,2
%N A231819 Least positive k such that k*n^2 - 1 is a prime, or 0 if no such k exists.
%t A231819 Table[k = 1; While[! PrimeQ[k*n^2 - 1], k++]; k, {n, 100}] (* _T. D. Noe_, Nov 18 2013 *)
%Y A231819 Cf. A035092 (least k such that k*(n^2)+1 is a prime).
%Y A231819 Cf. A175763 (least k such that k*(n^n)+1 is a prime).
%Y A231819 Cf. A035093 (least k such that k*n!+1 is a prime).
%Y A231819 Cf. A193807 (least k such that n*(k^2)+1 is a prime).
%Y A231819 Cf. A231119 (least k such that n*(k^k)+1 is a prime).
%Y A231819 Cf. A057217 (least k such that n*k!+1 is a prime).
%Y A231819 Cf. A034693 (least k such that n*k +1 is a prime).
%Y A231819 Cf. A231818 (least k such that k*(n^n)-1 is a prime).
%Y A231819 Cf. A083663 (least k such that k*n!-1 is a prime).
%Y A231819 Cf. A231734 (least k such that n*(k^2)-1 is a prime).
%Y A231819 Cf. A231735 (least k such that n*(k^k)-1 is a prime).
%Y A231819 Cf. A231820 (least k such that n*k!-1 is a prime).
%Y A231819 Cf. A053989 (least k such that n*k -1 is a prime).
%K A231819 nonn
%O A231819 1,1
%A A231819 _Alex Ratushnyak_, Nov 13 2013