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 A175391 #26 Aug 16 2025 15:12:06 %S A175391 1,36,100,196,225,256,441,484,676,1089,1156,1225,1296,1444,1521,2116, %T A175391 2601,3025,3249,3364,3844,4225,4761,5476,5929,6561,6724,7225,7396, %U A175391 7569,8281,8649,8836,9025,10000,11236,12321,13225,13924,14161,14884,15129 %N A175391 Perfect squares having a square number of divisors. %C A175391 From _Robert Israel_, Mar 20 2018: (Start) %C A175391 If m and n are coprime members of the sequence, then m*n is in the sequence. %C A175391 Includes all numbers of the forms p^(4*i*(i+1)) and p^(2*i)*q^(2*i) where p, q are distinct primes and i is a positive integer. (End) %H A175391 Robert Israel, <a href="/A175391/b175391.txt">Table of n, a(n) for n = 1..10000</a> %F A175391 a(n) = A063774(n)^2. - _Leroy Quet_, May 16 2010 %p A175391 with(numtheory): a := proc (n) if type(sqrt(tau(n^2)), integer) = true then n^2 else end if end proc: seq(a(n), n = 1 .. 130); # _Emeric Deutsch_, May 11 2010 %t A175391 Select[Range[150], IntegerQ[Sqrt[DivisorSigma[0, #^2]]]&]^2 (* _Vincenzo Librandi_, Mar 21 2018 *) %t A175391 Select[Range[150]^2,IntegerQ[Sqrt[DivisorSigma[0,#]]]&] (* _Harvey P. Dale_, Aug 16 2025 *) %o A175391 (PARI) isok(n) = issquare(n) && issquare(numdiv(n)); \\ _Michel Marcus_, Mar 21 2018 %Y A175391 Cf. A063774, A175050. - _Leroy Quet_, May 16 2010 %K A175391 nonn %O A175391 1,2 %A A175391 _Leroy Quet_, Apr 27 2010 %E A175391 Extended by _Emeric Deutsch_ and _Jon E. Schoenfield_, May 11 2010