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 A134407 #12 Sep 15 2014 14:12:04 %S A134407 3,5,7,8,9,11,12,13,15,17,18,19,21,22,23,25,27,28,29,30,31,32,33,34, %T A134407 35,37,38,39,41,42,43,44,45,46,47,48,49,50,51,52,53,55,57,58,59,60,61, %U A134407 62,63,64,65,67,68,69,70,71,72,73,75,76,77,78,79,80,81,82,83,85,86,87,88 %N A134407 Numbers n such that n^2 + 1 is composite. %F A134407 a(n) ~ n. - _Charles R Greathouse IV_, Sep 15 2014 %e A134407 a(1)=3, because 3^2 + 1 = 10 is composite, %e A134407 a(2)=5, because 5^2 + 1 = 26 is composite, %e A134407 a(3)=7, because 7^2 + 1 = 50 is composite. %p A134407 ts_fn2:=proc(n) local i,tren,ans; ans:=[ ]: for i from 1 to n do tren := i^(2)+1: if (isprime(tren) = false) then ans:=[ op(ans), i ]: fi od: RETURN(ans) end: ts_fn2(200); %t A134407 Select[Range@100,!PrimeQ[#^2+1]&] (* _Vladimir Joseph Stephan Orlovsky_, Feb 03 2012 *) %o A134407 (PARI) is(n)=!isprime(n^2+1) \\ _Charles R Greathouse IV_, Sep 15 2014 %Y A134407 Cf. A002496, A002808, A005574, A018252. %K A134407 nonn,easy %O A134407 1,1 %A A134407 _Jani Melik_, Jan 18 2008