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 A228115 #8 Feb 16 2025 08:33:20 %S A228115 3,21,143,1061,8366,68932,585881,5094722,45074595,404185377, %T A228115 3663479699,33498077106,308548877876,2859703657128,26646019345842, %U A228115 249434445759050,2344494354096166,22116172789221197,209301155352811190,1986521422431963549,18904049485198437478,180323870540071281301,1723847795281971132487,16512536418951055856540,158463448213030472998711 %N A228115 First differences of A227693. %C A228115 This sequence gives a good approximation of the number of primes with n digits (A006879); see (A228116). %D A228115 John H. Conway and R. K. Guy, The Book of Numbers, Copernicus, an imprint of Springer-Verlag, NY, 1996, page 144. %H A228115 Vladimir Pletser, <a href="/A228115/b228115.txt">Table of n, a(n) for n = 1..500</a> %H A228115 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/FibonacciPolynomial.html">Fibonacci Polynomial.</a> %F A228115 a(n)= A227693(n)- A227693(n-1) %e A228115 For n =1, A227693(1)- A227693(0) =4-1=3, where A227693(1)= round((F[3]( 1.016825…))^2)=4 with F[3](x) = x^2+1 and A227693(0)= round(F[1](x)) =1 with F[1](x)=1 %Y A228115 Cf. A006879, A228111 - A228116 %K A228115 nonn %O A228115 1,1 %A A228115 _Vladimir Pletser_, Aug 10 2013