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A078743
a(n) is the Fibonacci index of b(n) in the sequence b(1), b(2), ... where b(n) is the smallest Fibonacci number > b(n-1) such that b(1) + ... + b(n) is prime.
1
3, 4, 6, 9, 12, 24, 78, 108, 114, 213, 576, 1674, 1773, 1920, 2916, 23439, 24606
OFFSET
1,1
COMMENTS
A more compact version of A078742. a(7), if it exists, > 73, because A078742(7), if it exists, >10^15. - Neil Fernandez, Aug 22 2007
EXAMPLE
The smallest Fibonacci number to be prime is 2, the 3rd Fibonacci number, so a(1)=3. The smallest Fibonacci number >2 that yields a prime when added to 2 is 3, the 4th Fibonacci number, so a(2)=4. The smallest Fibonacci number >3 that yields a prime when added to 2+3 is 8, the 4th Fibonacci number, so a(3)=6.
MAPLE
N:= 16; # to get the first N terms
fib:= combinat[fibonacci]:
a[1]:= 3: s:= fib(3): count:= 1:
for i from 4 while count < N do
if isprime(s+fib(i)) then
count:= count+1;
a[count]:= i;
s:= s + fib(i);
fi
od:
seq(a[i], i=1..N); # Robert Israel, May 20 2014
CROSSREFS
Sequence in context: A241655 A288346 A373416 * A096846 A140570 A285303
KEYWORD
nonn
AUTHOR
Neil Fernandez, Dec 21 2002
EXTENSIONS
a(7) to a(17) from Robert Israel, May 20 2014
STATUS
approved