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 A177404 #18 Sep 08 2022 08:45:53 %S A177404 2,4,8,9,18,25,32,49,64,72,81,100,121,162,242,256,289,361,392,400,484, %T A177404 512,529,576,648,729,784,1058,1296,1352,1444,1681,1849,1922,2048,2116, %U A177404 2500,3136,3872,4418,4608,4624,5184,5776,5832,6889,7225,7396,7744 %N A177404 Numbers n such that n^2 minus (sum of the squares of the proper divisors of n) is a prime number. %C A177404 Sum of squares of proper divisors of n is given by A067558. %H A177404 Harvey P. Dale, <a href="/A177404/b177404.txt">Table of n, a(n) for n = 1..200</a> %e A177404 9 has proper divisors 3 and 1; it is in the list because 9^2-(3^2+1^2) = 71 is a prime number. %t A177404 Select[Range[8000],PrimeQ[#^2-Total[Most[Divisors[#]]^2]]&] (* _Harvey P. Dale_, Dec 14 2011 *) %o A177404 (Magma) a067558:=func< n | n le 1 select 0 else &+[ D[k]^2: k in [1..#D-1] ] where D is Divisors(n) >; [ n: n in [1..10000] | IsPrime(n^2-a067558(n)) ]; %Y A177404 Cf. A067558. %K A177404 nonn %O A177404 1,1 %A A177404 _Claudio Meller_, Dec 10 2010