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 A063509 #19 Sep 18 2024 11:23:14 %S A063509 2,1,3,7,11,29,47,123,199,322,521,843,2207,3571,9349,15127,39603, %T A063509 64079,103682,167761,271443,1149851,3010349,4870847,12752043,20633239, %U A063509 33385282,54018521,87403803,228826127,370248451,969323029,1568397607 %N A063509 Squarefree Lucas numbers. %H A063509 Harry J. Smith, <a href="/A063509/b063509.txt">Table of n, a(n) for n = 1..200</a> %t A063509 Select[LucasL[Range[0,50]],SquareFreeQ] (* _Harvey P. Dale_, Jan 20 2020 *) %o A063509 (PARI) for(n=0,50,my(x=fibonacci(n)+2*fibonacci(n-1)); if(issquarefree(x),print1(x, ", "))) %Y A063509 Cf. A000032. %K A063509 nonn %O A063509 1,1 %A A063509 _Jason Earls_, Aug 09 2001 %E A063509 More terms from _Dean Hickerson_, Aug 22 2001 %E A063509 Offset changed by _Andrew Howroyd_, Sep 18 2024