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Numbers k such that 2*A000005(k) = 3*A000005(k+1).
2

%I #19 Apr 09 2024 08:09:28

%S 4,20,32,45,50,68,76,92,117,124,212,236,261,325,333,338,350,412,436,

%T 452,477,578,596,608,620,628,644,650,668,716,722,740,788,801,804,825,

%U 836,855,860,884,892,916,925,932,964,968,981,1014,1017,1058,1076

%N Numbers k such that 2*A000005(k) = 3*A000005(k+1).

%H Amiram Eldar, <a href="/A172624/b172624.txt">Table of n, a(n) for n = 1..10000</a>

%F {k: 2*tau(k) = 3*tau(k+1)}.

%t Select[Range[1100],2*DivisorSigma[0,#]==3*DivisorSigma[0,#+1]&] (* _Harvey P. Dale_, Nov 06 2012 *)

%o (PARI) is(n) = 2 * numdiv(n) == 3 * numdiv(n+1); \\ _Amiram Eldar_, Apr 09 2024

%Y Subsequence of A059269.

%Y Cf. A000005, A172969.

%K nonn

%O 1,1

%A _Juri-Stepan Gerasimov_, Nov 21 2010

%E Corrected by _D. S. McNeil_, Nov 21 2010