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Number k such that k and k+1 have the same number of nonunitary divisors (A048105).
7

%I #7 May 16 2021 02:41:27

%S 1,2,5,6,10,13,14,21,22,27,29,30,33,34,37,38,41,42,44,46,57,58,61,65,

%T 66,69,70,73,75,77,78,82,85,86,93,94,98,101,102,105,106,109,110,113,

%U 114,116,118,122,124,129,130,133,135,137,138,141,142,145,147,154,157

%N Number k such that k and k+1 have the same number of nonunitary divisors (A048105).

%H Amiram Eldar, <a href="/A344314/b344314.txt">Table of n, a(n) for n = 1..10000</a>

%e 1 is a term since A048105(1) = A048105(2) = 0.

%e 27 is a term since A048105(27) = A048105(28) = 2.

%t nd[n_] := DivisorSigma[0, n] - 2^PrimeNu[n]; Select[Range[200], nd[#] == nd[# + 1] &]

%Y Cf. A048105, A064115, A335328, A344315.

%Y Similar sequences: A005237, A006049, A343819, A344312, A344313.

%K nonn

%O 1,2

%A _Amiram Eldar_, May 14 2021