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A304095 a(n) is the number of the proper divisors of n that are Lucas numbers larger than 3 (4, 7, 11, 18, ...). 5

%I #8 May 13 2018 20:43:31

%S 0,0,0,0,0,0,0,1,0,0,0,1,0,1,0,1,0,0,0,1,1,1,0,1,0,0,0,2,0,0,0,1,1,0,

%T 1,2,0,0,0,1,0,1,0,2,0,0,0,1,1,0,0,1,0,1,1,2,0,1,0,1,0,0,1,1,0,1,0,1,

%U 0,1,0,2,0,0,0,1,2,0,0,1,0,0,0,2,0,0,1,2,0,1,1,1,0,1,0,1,0,1,1,1,0,0,0,1,1,0,0,2,0,1,0,2,0,0,0,2,0,0,1,1

%N a(n) is the number of the proper divisors of n that are Lucas numbers larger than 3 (4, 7, 11, 18, ...).

%C a(n) is the number of the proper divisors d of n that are of the form d = A000045(k-1) + A000045(k+1), for k >= 3.

%H Antti Karttunen, <a href="/A304095/b304095.txt">Table of n, a(n) for n = 1..65537</a>

%F a(n) = Sum_{d|n, d>3, d<n} A102460(d).

%F a(n) = A007949(A304102(n)).

%e The proper divisors of 28 are 1, 2, 4, 7 and 14. Of these 4 and 7 are Lucas numbers (A000032) larger than 3, thus a(28) = 2.

%o (PARI)

%o A102460(n) = { my(u1=1,u2=3,old_u1); if(n<=2,sign(n),while(n>u2,old_u1=u1;u1=u2;u2=old_u1+u2);(u2==n)); };

%o A304095(n) = sumdiv(n,d,(d>3)*(d<n)*A102460(d));

%Y Cf. A000045, A000204, A102460, A304091, A304093, A304096, A304102.

%Y Cf. also A300836.

%K nonn

%O 1,28

%A _Antti Karttunen_, May 13 2018

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Last modified April 24 20:08 EDT 2024. Contains 371963 sequences. (Running on oeis4.)