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 A091098 #16 Feb 16 2025 08:32:52
%S A091098 1,11,80,609,4783,39175,332180,2880504,25423491,227523275,2059020280,
%T A091098 18803924340,173032709183,1602470783672,14922284735484,
%U A091098 139619168787795,1311778575685086,12369977142579584,117028833597800689,1110409801150582707
%N A091098 Number of primes of the form 4k+1 less than 10^n.
%H A091098 Marc Deléglise, Pierre Dusart, and Xavier-Francois Roblot, <a href="http://dx.doi.org/10.1090/S0025-5718-04-01649-7">Counting primes in residue classes</a>, Math. Comp. 73 (2004), no. 247, 1565-1575
%H A091098 Daniel Pareja, <a href="http://www.math.ubc.ca/~gerg/teaching/613-Winter2011/PrimeNumberRaces.pdf">Prime Number Races</a>
%H A091098 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/ModularPrimeCountingFunction.html">Modular Prime Counting Function</a>
%t A091098 cnt=0; k=0; Table[lim=10^n; While[4k+1<lim, If[ PrimeQ[4k+1], cnt++ ]; k++ ]; cnt, {n, 6}]
%Y A091098 Cf. A091099 (number of primes of the form 4k+3 less than 10^n).
%K A091098 nonn
%O A091098 1,2
%A A091098 _T. D. Noe_, Dec 19 2003
%E A091098 a(10)-a(16) from _Robert G. Wilson v_, Dec 22 2003
%E A091098 a(17)-a(20) from _Marc Deleglise_, Jun 28 2007