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 A188347 #26 Feb 09 2021 02:49:30 %S A188347 217073,671349,826827,1092750,1092751,1427373,2097051,2779373,3112822, %T A188347 3306447,3597726,3994823,4063777,4442877,4630547,4842477,5436378, %U A188347 5479622,5610647,5634125,6315022,6474223,6626322,6677867,7128474,7216621,7216622,7295451,7507926 %N A188347 Central element of a series of 7 successive nonsquarefree numbers. %C A188347 Each of a(n), a(n)-1, a(n)-2, a(n)-3, a(n)+1, a(n)+2, a(n)+3 has at least one square divisor. %H A188347 Amiram Eldar, <a href="/A188347/b188347.txt">Table of n, a(n) for n = 1..10000</a> %F A188347 a(n) = A077640(n) + 3. - _Amiram Eldar_, Feb 09 2021 %e A188347 217073=17*113^2, 217073-1=2^4*13567, 217073-2=3^2*89*271, 217073-3=2*5*7^2*443, 217073+1=2*3*11^2*13*23, 217073+2=5^2*19*457, 217073+3=2^2*54269. %t A188347 Select[Range[200000,5000000], !SquareFreeQ[#] &&!SquareFreeQ[#-1] &&!SquareFreeQ[#+1] &&!SquareFreeQ[#-2] &&!SquareFreeQ[#+2] &&!SquareFreeQ[#-3] &&!SquareFreeQ[#+3]&] %Y A188347 Cf. A005117, A013929, A077640, A188296. %K A188347 nonn %O A188347 1,1 %A A188347 _Vladimir Joseph Stephan Orlovsky_, Mar 29 2011 %E A188347 More terms from _Carl Najafi_, Aug 22 2011