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 A109561 #5 Jun 03 2025 01:08:16
%S A109561 199,211,317,1381,1759,1913,2161,2503,3089,3413,3947,5449,5717,5903,
%T A109561 6427,7129,8017,9349,9439,9697,10039,10111,10369,10567,11003,11329,
%U A109561 11633,11839,12073,12119,13009,13267,16007,16033,16193,16453,16493,16703,16763,16787,17053
%N A109561 prime(k) for those k where floor((2*(prime(k+1)-prime(k))*PrimePi(k) mod (8*k))/k) = m with m = 7.
%t A109561 a = Flatten[Table[If[Floor[2*Mod[(Prime[n + 1] - Prime[n])*PrimePi[n]/n, 8]] == 7, Prime[n], {}], {n, 1, 400}]]
%Y A109561 Cf. A000040, A000720, A001359.
%Y A109561 Cf. A109556-A109569 for m = 2..15.
%K A109561 nonn,less
%O A109561 1,1
%A A109561 _Roger L. Bagula_, Jun 27 2005
%E A109561 Name edited, offset corrected and more terms added by _Amiram Eldar_, Jun 02 2025