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%I #18 Sep 01 2020 08:55:18
%S 3,5,11,16,17,18,25,29,33,41,48,50,52,54,55,59,71,85,88,90,91,93,96,
%T 98,101,103,105,107,124,126,137,141,143,148,149,150,159,160,162,163,
%U 165,169,179,183,185,191,193,195,196,197,198,201,203,213,215,217,219,227
%N Numbers k such that mu(k) = mu(k+2), where mu is the Möbius function (A008683).
%C a(n) seems to be asymptotic to c*n with c near 3.73. Probably c = 1/(3A/2 + 1 - 12/Pi^2) ~ 3.729994018, where A ~ 0.322634099 is the product over all primes p of 1 - 2/p^2.
%H Amiram Eldar, <a href="/A074820/b074820.txt">Table of n, a(n) for n = 1..10000</a>
%e 3 is a term since mu(3) = mu(5) = -1.
%t Select[Range[230], MoebiusMu[ # ]==MoebiusMu[ #+2]&]
%t Flatten[Position[Partition[MoebiusMu[Range[250]],3,1],_?(#[[1]]==#[[3]]&),{1},Heads->False]] (* _Harvey P. Dale_, Mar 08 2015 *)
%Y Cf. A008683, A064148.
%K nonn
%O 1,1
%A _Benoit Cloitre_, Sep 08 2002
%E Edited by _Dean Hickerson_, Sep 10 2002
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