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%I #16 Mar 18 2023 10:36:14
%S 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,1,1,1,
%T 1,1,1,1,1,1,1,1,1,1,2,2,2,2,2,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,
%U 4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,5,5,5,5,5,5,5,5,5,5,5,5,5
%N Number of times 7 is the leading digit of the first n+1 Fibonacci numbers in decimal representation.
%H Winston de Greef, <a href="/A105517/b105517.txt">Table of n, a(n) for n = 0..10000</a>
%F a(n) = #{k: A008963(k) = 7 and 0<=k<=n};
%F a(A105507(n)) = a(A105507(n) - 1) + 1;
%F n = A105511(n) + A105512(n) + A105513(n) + A105514(n) + A105515(n) + A105516(n) + a(n) + A105518(n) + A105519(n).
%F a(n) ~ log_10(8/7) * n. - _Amiram Eldar_, Jan 12 2023
%t Accumulate[Table[If[IntegerDigits[Fibonacci[n]][[1]]==7,1,0],{n,0,120}]] (* _Harvey P. Dale_, Apr 29 2018 *)
%o (PARI)
%o (leadingdigit(n, b=10) = n \ 10^logint(n, b));
%o (isok(n) = leadingdigit(fibonacci(n))==7);
%o (lista(n)=my(a=vector(1+n), r=0); for (i=1, n, r+=isok(i); a[1+i]=r); a) \\ _Winston de Greef_, Mar 17 2023
%Y Cf. A000030, A000045, A008963, A105507.
%Y Cf. A105511, A105512, A105513, A105514, A105515, A105516, A105518, A105519.
%K nonn,base
%O 0,45
%A _Reinhard Zumkeller_, Apr 11 2005
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