%I A027862
%S A027862 5,13,41,61,113,181,313,421,613,761,1013,1201,1301,1741,1861,2113,
%T A027862 2381,2521,3121,3613,4513,5101,7321,8581,9661,9941,10513,12641,
%U A027862 13613,14281,14621,15313,16381,19013,19801,20201,21013,21841,23981,24421,
               26681
%N A027862 Primes of the form n^2 + (n+1)^2; or, primes of the form (n^2+1)/2.
%C A027862 Also, primes of the form 4n+1 which are the hypotenuse of one and only 
               one right triangle with integral arms. - Cino Hilliard (hillcino368(AT)gmail.com), 
               Mar 16 2003
%C A027862 Centered square primes (i.e. prime terms of centered squares A001844). 
               - Lekraj Beedassy (blekraj(AT)yahoo.com), Jan 21 2005
%D A027862 D. M. Burton, Elementary Number Theory, Allyn and Bacon Inc. Boston, 
               MA, 1976, p. 271.
%D A027862 Morris Kline, Mathematical Thought from Ancient to Modern Times, 1972. 
               pp. 275.
%H A027862 T. D. Noe, <a href="b027862.txt">Table of n, a(n) for n=1..1000</a>
%H A027862 P. De Geest, <a href="http://www.worldofnumbers.com/index.html">World!Of 
               Numbers</a>
%t A027862 lst={};Do[If[PrimeQ[p=n^2+(n+1)^2], (*Print[p];*)AppendTo[lst, p]], {n, 
               10^3}];lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Aug 
               21 2008]
%o A027862 (PARI) je=[]; for(n=1,500, if(isprime(n^2+(n+1)^2),je=concat(je,n^2+(n+1)^2))); 
               je
%o A027862 (PARI) fermat(n) = { for(x=1,n, y=2*x*(x+1)+1; if(isprime(y),print1(y" 
               ")) ) }
%Y A027862 Primes p such that A079887(p)=1
%Y A027862 Primes arising in A002731, A027861, A091277 gives prime index.
%Y A027862 Sequence in context: A025490 A087938 A103729 this_sequence A100210 A080267 
               A034735
%Y A027862 Adjacent sequences: A027859 A027860 A027861 this_sequence A027863 A027864 
               A027865
%K A027862 nonn,easy,nice
%O A027862 1,1
%A A027862 Patrick De Geest (pdg(AT)worldofnumbers.com)
%E A027862 More terms from Cino Hilliard (hillcino368(AT)gmail.com), Mar 16 2003