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 A072520 Index of smallest Fibonacci number beginning with the n-th Fibonacci number other than itself. 1

%I

%S 7,7,8,9,10,11,31,32,76,77,78,79,525,1416,1417,1863,1864,6004,6005,

%T 6006,6007,6008,6009,70009,70010,70011,3853341,8668488,11420001,

%U 13139697,14515454,15203333,15547273,15891213,15891214,15891215,15891216,63908693,63908694,239743481

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

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

%p N:= 30: # attempt to get a(1)..a(N)

%p V:= Vector(N):

%p V:= 7:

%p count:= 1;

%p F:= Vector(N,combinat:-fibonacci):

%p L:= ilog10(F[N]):

%p tmin:= F:

%p a:= 1: b:= 1:

%p for n from 3 to 10^5 while count < N do

%p c:= a+b;

%p a:= b; b:= c;

%p v:= floor(c/10^(max(1,ilog10(c)-L)));

%p while v >= tmin do

%p j:= ListTools:-BinarySearch(F, v);

%p if j > 0 and j <= N and V[j] = 0 then

%p count:= count+1;

%p V[j]:= n;

%p jm:= min(select(t -> V[t]=0, [\$1..N]));

%p tmin:= F[jm];

%p fi;

%p v:= floor(v/10);

%p od:

%p od:

%p seq(V[i],i=1..jm-1); # _Robert Israel_, Mar 20 2018

%Y Cf. A072519.

%K base,nonn

%O 1,1

%A _Amarnath Murthy_, Jul 31 2002

%E Corrected and extended by _Sascha Kurz_, Jan 03 2003

%E a(24)-a(26) from _Robert Israel_, Mar 20 2018

%E a(27)-a(40) from _Giovanni Resta_, Aug 26 2018

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Last modified September 22 22:24 EDT 2020. Contains 337291 sequences. (Running on oeis4.)