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%I #32 Jan 24 2022 04:16:27
%S 2,4,10,18,36,62,90,902,1214,2936,3436,325726,378646,646840,5432174,
%T 273222344,285775216,1411668430,1416411790,2586905784
%N Even numbers whose sum of proper divisors is a Fibonacci number.
%C What is the asymptotic behavior of this sequence?
%C No more terms below 10^10. - _Amiram Eldar_, Oct 18 2019
%e 18 is a term because 1 + 2 + 3 + 6 + 9 = 21 is a Fibonacci number.
%o (PARI) isFibonacci(n)=my(k=n^2); issquare(k+=(k+1)<<2) || (n>0 && issquare(k-8));
%o is(n)=isFibonacci(sigma(n)-n)&&n%2==0
%Y Cf. A000045, A001065, A272412.
%K nonn,more
%O 1,1
%A _Altug Alkan_, Dec 16 2016
%E a(18)-a(20) from _Amiram Eldar_, Oct 18 2019
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