OFFSET
1,4
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..10946
FORMULA
a(n) = Sum_{d|n, d<n} A010056(d).
G.f.: Sum_{k>=2} x^(2*Fibonacci(k)) / (1 - x^Fibonacci(k)). - Ilya Gutkovskiy, Apr 14 2021
EXAMPLE
For n = 55, its proper divisors are [1, 5, 11], of which only two, namely 1 and 5 are in A000045, thus a(55) = 2.
MATHEMATICA
With[{s = Fibonacci@ Range[2, 40]}, Table[DivisorSum[n, 1 &, And[MemberQ[s, #], # != n] &], {n, 105}]] (* Michael De Vlieger, Oct 09 2017 *)
PROG
(PARI)
A010056(n) = { my(k=n^2); k+=(k+1)<<2; (issquare(k) || (n>0 && issquare(k-8))) }; \\ This function from Charles R Greathouse IV, Jul 30 2012
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Oct 09 2017
STATUS
approved