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 A139430 #9 Apr 17 2019 19:06:42
%S A139430 3,5,11,5,11,11,17,19,23,97,127,1009,167,269,953,479,3307,1453,37507,
%T A139430 2357,599,17669,5527,3191,3251,70249,147773
%N A139430 Smallest prime p such that M(n)^2+p*M(n)-1 is prime with M(n)= Mersenne primes =A000668(n).
%C A139430 All primes certified using openpfgw_v12 from primeform group
%e A139430 3*3+3*3-1=17 prime 3=M(1)=2^2-1 so p(1)=3;
%e A139430 7*7+5*7-1=83 prime 7=M(2)=2^3-1 so p(2)=5:
%e A139430 31*31+11*31-1=1301 prime 31=M(3)=2^5-1 so p(3)=11.
%t A139430 A000043 = {2, 3, 5, 7, 13, 17, 19, 31, 61, 89, 107, 127, 521, 607, 1279, 2203, 2281, 3217, 4253, 4423, 9689, 9941, 11213, 19937, 21701, 23209, 44497, 86243, 110503, 132049, 216091, 756839, 859433, 1257787, 1398269, 2976221, 3021377, 6972593, 13466917, 20996011, 24036583, 25964951, 30402457, 32582657, 37156667, 42643801, 43112609};
%t A139430 Table[m = 2^A000043[[n]] - 1; m2 = m^2; p = 1;
%t A139430 While[! PrimeQ[m2 + Prime[p]*m - 1], p++]; Prime[p], {n, 18}] (* _Robert Price_, Apr 17 2019 *)
%Y A139430 Cf. A000668, A139424, A139425, A139426, A139427, A139428, A139429, A139431.
%K A139430 hard,more,nonn
%O A139430 1,1
%A A139430 _Pierre CAMI_, Apr 21 2008