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 A245472 #13 Nov 23 2019 02:47:26 %S A245472 0,1,0,1,0,2,1,2,0,1,11,5,3,5,5,7,9,7,33,199,39,149,109,3,245,233,263, %T A245472 3425,5,1057,1889,725,2223,1559,1711,485,5019,15979,1329,7727,6661, %U A245472 4833,25667,8177,4973,45233,8033,11429,23567,10111,9465,141625,43139,56175 %N A245472 Number of composite Lucas numbers between the prime Lucas numbers A005479(n) and A005479(n+1). %H A245472 Jens Kruse Andersen, <a href="/A245472/b245472.txt">Table of n, a(n) for n = 1..63</a> %F A245472 a(n) = A001606(n+1) - A001606(n) - 1, for n > 1. %e A245472 a(1)=0 because A005479(1)= 2, A005479(2)= 3 and there are no composite Lucas number between 2 and 3 (the number 1 is not composite). %e A245472 a(6)=2 because A005479(6)= 47, A005479(7)= 199 and there are 2 composite Lucas numbers between 47 and 199: 76 = 2^2*19 and 123 = 3*41. %p A245472 with(combinat,fibonacci):with(numtheory):i:=0:a:=n->2*fibonacci(n-1)+fibonacci(n):for n from 3 to 100 do:if type (a(n), prime)=true then printf(`%d, `, i):i:=0:else i:=i+1:fi:od: %Y A245472 Cf. A000032, A001606, A245470. %K A245472 nonn %O A245472 1,6 %A A245472 _Michel Lagneau_, Jul 23 2014