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 A249777 #5 Nov 06 2014 00:14:58 %S A249777 0,0,0,1,0,1,2,1,2,3,0,5,6,0,6,7,3,2,10,1,5,6,3,7,10,0,10,13,0,13,16, %T A249777 0,5,15,1,11,16,1,6,15,2,11,16,4,16,17,2,17,12,5,16,17,3,17,18,0,20, %U A249777 21,0,23,28,0,23,27,1,15,30,3,17,26,4,19,28,2,21 %N A249777 Let z = A084937: a(n) = number of numbers <= z(n) that are != z(k) for k=1..n-1 and not coprime to z(n-1) and z(n-2). %C A249777 a(A249684(n)) = 0. %H A249777 Reinhard Zumkeller, <a href="/A249777/b249777.txt">Table of n, a(n) for n = 1..10000</a> %e A249777 . n | A084937(n) | unused numbers less than A084937(n) | a(n) %e A249777 . ----+------------+------------------------------------------+----- %e A249777 . 3 | 3 | _ | 0 %e A249777 . 4 | 5 | 4 | 1 %e A249777 . 5 | 4 | _ | 0 %e A249777 . 6 | 7 | 6 | 1 %e A249777 . 7 | 9 | 6, 8 | 2 %e A249777 . 8 | 8 | 6 | 1 %e A249777 . 9 | 11 | 6, 10 | 2 %e A249777 . 10 | 13 | 6, 10, 12 | 3 %e A249777 . 11 | 6 | _ | 0 %e A249777 . 12 | 17 | 10, 12, 14, 15, 16 | 5 %e A249777 . 13 | 19 | 10, 12, 14, 15, 16, 18 | 6 %e A249777 . 14 | 10 | _ | 0 %e A249777 . 15 | 21 | 12, 14, 15, 16, 18, 20 | 6 %e A249777 . 16 | 23 | 12, 14, 15, 16, 18, 20, 22 | 7 %e A249777 . 17 | 16 | 12, 14, 15 | 3 %e A249777 . 18 | 15 | 12, 14 | 2 %e A249777 . 19 | 29 | 12, 14, 18, 20, 22, 24, 25, 26, 27, 28 | 10 %e A249777 . 20 | 14 | 12 | 1 %e A249777 . 21 | 25 | 12, 18, 20, 22, 24 | 5 %e A249777 . 22 | 27 | 12, 18, 20, 22, 24, 26 | 6 %e A249777 . 23 | 22 | 12, 18, 20 | 3 %e A249777 . 24 | 31 | 12, 18, 20, 24, 26, 28, 30 | 7 %e A249777 . 25 | 35 | 12, 18, 20, 24, 26, 28, 30, 32, 33, 34 | 10 . %o A249777 (Haskell) %o A249777 a249777 n = a249777_list !! (n-1) %o A249777 a249777_list = 0 : 0 : f 2 1 [3..] where %o A249777 f x y zs = g zs 0 where %o A249777 g (u:us) w | gcd y u > 1 || gcd x u > 1 = g us (w + 1) %o A249777 | otherwise = w : f u x (delete u zs) %Y A249777 Cf. A084937, A249684. %K A249777 nonn %O A249777 1,7 %A A249777 _Reinhard Zumkeller_, Nov 05 2014