A072520 Index of smallest Fibonacci number beginning with the n-th Fibonacci number other than itself.

7, 7, 8, 9, 10, 11, 31, 32, 76, 77, 78, 79, 525, 1416, 1417, 1863, 1864, 6004, 6005, 6006, 6007, 6008, 6009, 70009, 70010, 70011, 3853341, 8668488, 11420001, 13139697, 14515454, 15203333, 15547273, 15891213, 15891214, 15891215, 15891216, 63908693, 63908694, 239743481

Offset

1,1

Links

Table of n, a(n) for n=1..40.

Example

a(6) = 11 as the 11th Fibonacci number 89 begins with 8, the 6th Fibonacci number.

Maple

N:= 30: # attempt to get a(1)..a(N)
V:= Vector(N):
V[1]:= 7:
count:= 1;
F:= Vector(N, combinat:-fibonacci):
L:= ilog10(F[N]):
tmin:= F[1]:
a:= 1: b:= 1:
for n from 3 to 10^5 while count < N do
  c:= a+b;
  a:= b; b:= c;
  v:= floor(c/10^(max(1, ilog10(c)-L)));
  while v >= tmin do
    j:= ListTools:-BinarySearch(F, v);
    if j > 0 and j <= N and V[j] = 0 then
      count:= count+1;
      V[j]:= n;
      jm:= min(select(t -> V[t]=0, [$1..N]));
      tmin:= F[jm];
    fi;
    v:= floor(v/10);
  od:
od:
seq(V[i], i=1..jm-1); # Robert Israel, Mar 20 2018

Crossrefs

Cf. A072519.

Sequence in context: A108186 A024818 A076236 * A187179 A110941 A182470

Adjacent sequences: A072517 A072518 A072519 * A072521 A072522 A072523

Keyword

base,nonn

Author

Amarnath Murthy, Jul 31 2002

Extensions

Corrected and extended by Sascha Kurz, Jan 03 2003

a(24)-a(26) from Robert Israel, Mar 20 2018

a(27)-a(40) from Giovanni Resta, Aug 26 2018

Status

approved