OFFSET
1,3
LINKS
Thomas R. Nicely, Some Results of Computational Research in Prime Numbers [See local copy in A007053]
Tomás Oliveira e Silva, Tables of values of pi(x) and of pi2(x)
EXAMPLE
a(2) = 1 because there is 1 prime less than 100 whose initial digit is 9, i.e., 97.
MATHEMATICA
f[n_] := f[n] = PrimePi[10^(n + 1)] - PrimePi[9*10^n] + f[n - 1]; f[0] = 0; Table[f[n], {n, 0, 12}]
CROSSREFS
KEYWORD
base,hard,nonn
AUTHOR
Shyam Sunder Gupta, Aug 14 2002
EXTENSIONS
Edited and extended by Robert G. Wilson v, Aug 29 2002
a(20)-a(22) added by David Baugh, Mar 22 2015
STATUS
approved