OFFSET
1,1
COMMENTS
What is the asymptotic behavior of this sequence?
No more terms below 10^10. - Amiram Eldar, Oct 18 2019
EXAMPLE
18 is a term because 1 + 2 + 3 + 6 + 9 = 21 is a Fibonacci number.
PROG
(PARI) isFibonacci(n)=my(k=n^2); issquare(k+=(k+1)<<2) || (n>0 && issquare(k-8));
is(n)=isFibonacci(sigma(n)-n)&&n%2==0
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Altug Alkan, Dec 16 2016
EXTENSIONS
a(18)-a(20) from Amiram Eldar, Oct 18 2019
STATUS
approved