A077448 Numbers k such that Sum_{d|k} mu(d)*mu(k/d)^2 = +1.
1, 36, 100, 196, 225, 441, 484, 676, 1089, 1156, 1225, 1444, 1521, 2116, 2601, 3025, 3249, 3364, 3844, 4225, 4761, 5476, 5929, 6724, 7225, 7396, 7569, 8281, 8649, 8836, 9025, 11236, 12321, 13225, 13924, 14161, 14884, 15129, 16641, 17689, 17956
Offset: 1
Keywords
Links
- Amiram Eldar, Table of n, a(n) for n = 1..10000
Programs
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Mathematica
Select[Range[135], MoebiusMu[#] == 1 &]^2 (* Amiram Eldar, Jul 16 2020 *)
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PARI
is(n)=if(!issquare(n,&n),return(0)); my(f=factor(n)[,2]); if(n>1, #f%2==0 && vecmax(f)==1, n==1) \\ Charles R Greathouse IV, Oct 16 2015
Formula
a(n) = A030229(n)^2.
Sum_{n>=1} 1/a(n) = 21/(2*Pi^2). - Amiram Eldar, Jul 16 2020