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%I #23 Dec 02 2023 09:12:19
%S 2,3,6,9,15,17,21,28,30,36,43,46,47,51,54,62,69,71,72,75,80,90,92,93,
%T 96,99,101,102,107,108,109,110,114,118,120,122,124,133,135,141,150,
%U 151,152,156,160,161,164,170,171,174,196,197,206,207,208,210,212,216,223,226,231,235,236,238
%N Numbers k such that tau(2k-1) = tau(2k+1) where tau(k) = A000005(k).
%H Amiram Eldar, <a href="/A190276/b190276.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1000 from Harvey P. Dale)
%F A000005(2*a(n)-1) = A000005(2*a(n)+1).
%F a(n) = (A066692(n) + 1)/2. - _Michel Marcus_, Jan 04 2016
%t nn=250;With[{tau=DivisorSigma[0,Range[2nn+1]]},Select[Range[nn], tau[[2#-1]] == tau[[2#+1]]&]] (* _Harvey P. Dale_, May 19 2012 *)
%o (Magma) [n: n in [1..300] | NumberOfDivisors(2*n-1) eq NumberOfDivisors(2*n+1)]; // _Vincenzo Librandi_, Jan 03 2016
%o (PARI) isok(n) = numdiv(2*n-1)==numdiv(2*n+1); \\ _Michel Marcus_, Jan 04 2016
%Y Cf. A000005, A066692.
%K nonn,easy
%O 1,1
%A _Juri-Stepan Gerasimov_, May 07 2011
%E Corrected by _Harvey P. Dale_, May 19 2012
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