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%I #17 Sep 24 2018 02:40:07
%S 1,49,121,169,361,529,841,961,1849,2209,2809,5329,6889,9409,10609,
%T 12769,16129,24649,32041,38809,39601,49729,51529,54289,57121,58081,
%U 63001,66049,73441,78961,96721,99856,100489,110889,124609,151321,160801
%N Squares in A076361.
%H Giovanni Resta, <a href="/A115557/b115557.txt">Table of n, a(n) for n = 1..10000</a>
%F The commutator [sigma, tau] is zero, that is, A076360(x) = 0 and x is a square.
%e The special squared prime 121 is a term because it is a square and sigma(tau(121)) = sigma(3) = 4 = tau(sigma(121)) = tau(1 + 11 + 121) = tau(133) = 4.
%e The first solution with composite square root is 316^2 = 99856: tau(99856) = 15, sigma(15) = 24 or sigma(99856) = 195951 = 3*7*7*31*43, tau(195951) = 24.
%t ds = DivisorSigma; Select[Range[1000]^2, ds[0, ds[1, #]] == ds[1, ds[0, #]] &] (* _Giovanni Resta_, Apr 29 2017 *)
%o (PARI) isok(n) = issquare(n) && (sigma(numdiv(n)) == numdiv(sigma(n))); \\ _Michel Marcus_, Dec 20 2013
%Y Cf. A000005, A000203, A062068, A062069, A076360, A076361, A115558.
%K nonn
%O 1,2
%A _Labos Elemer_, Jan 25 2006
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