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%I #19 Jun 04 2022 04:30:17
%S 1,1,2,1,2,1,2,2,2,1,2,1,2,2,3,1,2,1,2,2,2,1,2,2,2,2,3,1,2,1,2,2,2,1,
%T 3,1,2,2,3,1,2,1,2,3,2,1,2,2,2,2,3,1,2,1,2,2,2,1,2,1,2,2,4,2,3,1,2,2,
%U 2,1,2,1,2,2,3,1,2,1,2,3,2,1,2,2,2,2,3,1,2,2,2,2,2,1,3,1,2,2,4,1,2,1,2,3,2
%N Number of divisors d of n such that d+1 is also a divisor of n+1.
%C The partial sums of this sequence from k = 1 to 10^m, for m = 1, 2, ..., are 15, 185, 1952, 19852, 199538, 1998538, 19995362, 199985379, 1999953823, ... . Conjecture: The asymptotic mean of this sequence is 2. - _Amiram Eldar_, Jun 04 2022
%H Antti Karttunen, <a href="/A082477/b082477.txt">Table of n, a(n) for n = 1..16384</a>
%F G.f.: Sum_{k>0} x^k/(1-x^(k*(k+1))). - _Vladeta Jovovic_, Apr 21 2010
%t ndd[n_]:=Count[Divisors[n],_?(Divisible[n+1,#+1]&)]; Array[ndd,110] (* _Harvey P. Dale_, Aug 29 2015 *)
%o (PARI) a(n)=sumdiv(n,d,if((n+1)%(d+1),0,1))
%Y Cf. A082478.
%K nonn
%O 1,3
%A _Benoit Cloitre_, Apr 27 2003
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