A279359 Even numbers whose sum of proper divisors is a Fibonacci number.

2, 4, 10, 18, 36, 62, 90, 902, 1214, 2936, 3436, 325726, 378646, 646840, 5432174, 273222344, 285775216, 1411668430, 1416411790, 2586905784, 34620518734, 564515976926, 811882646208, 1326864647898, 1548008754928, 2063984735284, 28933238284712, 29040521400152, 31260018191912, 31586954074712, 160595113092766, 164736642645358, 180312970059936

Offset: 1

Author

Altug Alkan, Dec 16 2016

Keywords

• nonn

Comments

What is the asymptotic behavior of this sequence?

Examples

			18 is a term because 1 + 2 + 3 + 6 + 9 = 21 is a Fibonacci number.
		

Crossrefs

Cf. A000045, A001065, A235710, A272412.

Programs

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

Extensions

a(18)-a(20) from Amiram Eldar, Oct 18 2019

a(21)-a(33) from Max Alekseyev, May 23 2025