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 A293428 #9 Oct 16 2017 19:58:40 %S A293428 1,2,2,3,4,5,4,5,6,7,8,8,8,9,10,10,11,12,12,13,13,14,15,16,16,17,18, %T A293428 19,20,20,20,20,21,21,22,23,23,24,24,25,26,27,26,26,27,28,29,29,30,31, %U A293428 32,32,33,34,35,36,36,37,38,39,39,39,40,41,42,42,43,44,44,44,45,46,46,47,47,48,49,50,50,51,52,52,53,53 %N A293428 a(0) = 1; and for n > 0, a(n) = a(n-1) + (A008966(4n+1) - A107078(4n+3)). %C A293428 After a(0)=1, each term a(n) is either (a) one more than its predecessor, in case 4n+1 and 4n+3 are both squarefree, (b) stays same if only the other one is squarefree, or (c) decreases by one if neither 4n+1 nor 4n+3 are squarefree. %H A293428 Antti Karttunen, <a href="/A293428/b293428.txt">Table of n, a(n) for n = 0..10000</a> %F A293428 a(0) = 1; and for n > 0, a(n) = a(n-1) + -1+(A008966(4n+1)+A008966(4n+3)). %F A293428 Or for n > 0, a(n) = a(n-1) + (A008966(4n+1) - A107078(4n+3)). %o A293428 (Scheme, with memoization-macro definec) %o A293428 (definec (A293428 n) (if (zero? n) 1 (+ -1 (A008966 (+ 1 (* 4 n))) (A008966 (+ 3 (* 4 n))) (A293428 (- n 1))))) %Y A293428 Cf. A008966, A107078, A293229, A293429. %Y A293428 Cf. also A293517. %K A293428 nonn %O A293428 0,2 %A A293428 _Antti Karttunen_, Oct 16 2017