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 A134427 #16 Feb 22 2021 03:41:41 %S A134427 3,5,8,9,11,12,13,15,17,19,21,22,23,25,27,28,29,30,31,33,34,35,37,39, %T A134427 42,44,45,46,47,48,49,50,51,52,53,55,58,59,60,61,62,63,64,65,67,69,71, %U A134427 72,73,75,76,77,78,79,80,81,83,85,86,87,88,89,91,92,95,96,97,98,100,101 %N A134427 Numbers k such that k^2 + 1 is a composite squarefree number. %H A134427 Amiram Eldar, <a href="/A134427/b134427.txt">Table of n, a(n) for n = 1..10000</a> %e A134427 a(1)=3, because 3^2 + 1 = 10 is composite squarefree. %e A134427 a(2)=5, because 5^2 + 1 = 26 is composite squarefree. %e A134427 a(3)=8, because 8^2 + 1 = 50 is composite squarefree. %p A134427 ts_fn4:=proc(n) local i,tren,ans; ans:=[ ]: for i from 1 to n do tren := i^(2)+1: if (isprime(tren) = false and numtheory[mobius] (tren) <> 0 ) then ans:=[ op(ans), i ]: fi od: RETURN(ans) end: ts_fn4(200); %t A134427 Select[Range[100], CompositeQ[#^2+1] && SquareFreeQ[#^2+1] &] (* _Amiram Eldar_, Feb 22 2021 *) %Y A134427 Cf. A002496, A124809, A134420. %K A134427 nonn %O A134427 1,1 %A A134427 _Jani Melik_, Jan 18 2008 %E A134427 Definition corrected by _T. D. Noe_, Sep 16 2008