

A073516


Number of primes less than 10^n with initial digit 2.


2



1, 3, 19, 146, 1129, 9142, 77025, 664277, 5837665, 52064915, 469864125, 4281198201, 39319600765, 363545360347, 3380562309312, 31590949437540, 296487794277035, 2793170342851930, 26402713858800478, 250324979315879678, 2379753569255122805, 22678735843184786383
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OFFSET

1,2


LINKS

Table of n, a(n) for n=1..22.
Thomas R. Nicely, Some Results of Computational Research in Prime Numbers
Tomás Oliveira e Silva, Tables of values of pi(x) and of pi2(x)


EXAMPLE

a(2)=3 because there are 3 primes up to 10^2 whose initial digit is 2 (namely 2, 23 and 29).


MATHEMATICA

f[n_] := f[n] = PrimePi[3*10^n]  PrimePi[2*10^n] + f[n  1]; f[0] = 1; Table[ f[n], {n, 0, 13}]


CROSSREFS

Cf. A073509 to A073517, their sum is A006880.
Sequence in context: A058859 A095002 A080833 * A005258 A131551 A074546
Adjacent sequences: A073513 A073514 A073515 * A073517 A073518 A073519


KEYWORD

base,hard,nonn


AUTHOR

Shyam Sunder Gupta, Aug 14 2002


EXTENSIONS

Edited and extended by Robert G. Wilson v, Aug 29 2002
a(21)a(22) added by David Baugh, Mar 21 2015


STATUS

approved



