A072912 Number of Fibonacci numbers F(k) <= 10^n which end in 0.

1, 1, 1, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 5, 5, 5, 6, 6, 6, 7, 7, 7, 8, 8, 8, 9, 9, 9, 10, 10, 10, 11, 11, 11, 11, 12, 12, 12, 13, 13, 13, 14, 14, 14, 15, 15, 15, 16, 16, 16, 17, 17, 17, 18, 18, 18, 18, 19, 19, 19, 20, 20, 20, 21, 21, 21, 22, 22, 22, 23, 23, 23, 24, 24, 24, 25, 25, 25

Offset: 0

Author

Shyam Sunder Gupta and Benoit Cloitre, Aug 15 2002

Keywords

• base
• nonn

Examples

			a(2)=6 because there are 6 Fibonacci numbers F(k) <= 10^2 which end in 0.
		

Crossrefs

Different from A002280.

Cf. A008597, A214855.

Programs

PARI

a(n) = (sum(i=0,ceil(n*log(10)/log((1+sqrt(5))/2)),if(fibonacci(i)%10+1+sign(fibonacci(i)-10^n),0,1)))

Formula

a(n) = ceiling(n*log(10)/(15*log(phi))) +0 or +1.