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 A160393 #19 Jun 16 2022 10:24:53 %S A160393 1,2,4,7,11,20,34,58,100,172,298,516,893,1547,2679,4640,8036,13918, %T A160393 24107,41754,72320,125262,216960,375786,650880,1127357,1952639, %U A160393 3382070,5857917,10146210,17573751,30438629,52721251,91315885,158163753,273947655,474491257,821842965 %N A160393 Square root of A003462, rounded up. %C A160393 This sequence gives a lower bound for A090246. A003462 is the number of points in P(Z/3Z)^n. If a subset of P(Z/3Z)^n contains m points with no 3 collinear, then there are at most 2*C(m,2) points which are collinear with 2 points of the subset. Therefore if m + 2*C(m,2) = m^2 < A003462(n) we can add at least one more point to the set. %H A160393 Chai Wah Wu, <a href="/A160393/b160393.txt">Table of n, a(n) for n = 1..1000</a> %F A160393 a(n) = ceiling(sqrt((3^n-1)/2)). %o A160393 (PARI) a(n) = sqrtint((3^n-3)/2)+1; \\ _Michel Marcus_, Oct 20 2016; corrected Jun 15 2022 %Y A160393 Cf. A090246, A003462. %K A160393 easy,nonn %O A160393 1,2 %A A160393 _Jack W Grahl_, May 12 2009