# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/

Search: id:a074216
Showing 1-1 of 1

%I A074216 #27 Sep 08 2022 08:45:07
%S A074216 49,169,196,361,441,676,784,961,1225,1369,1444,1521,1764,1849,2704,
%T A074216 3136,3249,3721,3844,3969,4225,4489,4900,5329,5476,5776,5929,6084,
%U A074216 6241,7056,7396,8281,8649,9025,9409,10609,10816,11025,11881,12321,12544
%N A074216 Squares satisfying sigma(n)==0 (mod 3).
%C A074216 Seems to contain all numbers of form k^2*p^2 where p are primes in A002476, k is not congruent to p and >=1.
%C A074216 Squares in A067051. - _Michel Marcus_, Dec 26 2013
%H A074216 Amiram Eldar, <a href="/A074216/b074216.txt">Table of n, a(n) for n = 1..10000</a>
%F A074216 Conjecture: a(n) = A072864(n)^2. - _R. J. Mathar_, May 19 2020
%p A074216 with(numtheory); A074216:=n->`if`(1-ceil(sigma(n^2)/3)+floor(sigma(n^2)/3)=1,n^2,NULL); seq(A074216(n), n=1..200); # _Wesley Ivan Hurt_, Dec 06 2013
%t A074216 Select[Range[150]^2,Divisible[DivisorSigma[1,#],3]&] (* _Harvey P. Dale_, Jul 10 2012 *)
%o A074216 (PARI) isok(n) = issquare(n) && !(sigma(n) % 3); \\ _Michel Marcus_, Aug 17 2019
%o A074216 (Magma) [n: n in [1..14161]|IsSquare(n) and DivisorSigma(1,n) mod 3 eq 0 ]; // _Marius A. Burtea_, Aug 17 2019
%Y A074216 Cf. A067051, A065764.
%K A074216 nonn
%O A074216 1,1
%A A074216 _Benoit Cloitre_, Sep 17 2002

# Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE