%I #19 Oct 28 2021 12:59:31
%S 0,1,15,127,1006,8230,70320,614821,5453140,48982456,444608278,
%T 4070532710,37535715441,348245215460,3247889171908,30429496751905,
%U 286235215995588,2702000272361599,25586688305447928,242978340446949438,2313264023790027111,22074118786158858975
%N Number of primes less than 10^n with initial digit 9.
%H Thomas R. Nicely, <a href="https://faculty.lynchburg.edu/~nicely/index.html">Some Results of Computational Research in Prime Numbers</a> [See local copy in A007053]
%H Tomás Oliveira e Silva, <a href="http://sweet.ua.pt/tos/primes.html">Tables of values of pi(x) and of pi2(x)</a>
%e a(2) = 1 because there is 1 prime less than 100 whose initial digit is 9, i.e., 97.
%t f[n_] := f[n] = PrimePi[10^(n + 1)] - PrimePi[9*10^n] + f[n - 1]; f[0] = 0; Table[f[n], {n, 0, 12}]
%Y A006880(n) = A073509(n)+ ... + A073516(n)+A073517(n-1).
%Y For primes with initial digit d (1 <= d <= 9) see A045707, A045708, A045709, A045710, A045711, A045712, A045713, A045714, A045715; A073517, A073516, A073515, A073514, A073513, A073512, A073511, A073510, A073509
%K base,hard,nonn
%O 1,3
%A _Shyam Sunder Gupta_, Aug 14 2002
%E Edited and extended by _Robert G. Wilson v_, Aug 29 2002
%E a(20)-a(22) added by _David Baugh_, Mar 22 2015