A091121 - OEIS

A091121

Number of primes of the form 7k+2 less than 10^n.

1, 4, 27, 203, 1584, 13065, 110771, 960114, 8474796, 75841428, 686342043, 6267979692, 57677527046, 534156912056, 4974094938312, 46539722172584, 437259525297523, 4123325710529002, 39009611212184786

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OFFSET

1,2

COMMENTS

Computed by T. D. Noe, Dec 19 2003

LINKS

Table of n, a(n) for n=1..19.

Eric Weisstein's World of Mathematics, Modular Prime Counting Function

MATHEMATICA

p = Select[Table[7 i + 2, {i, 0, 10^7}], PrimeQ[#] &]; Table[Count[p, x_ /; x < 10^n], {n, 7}] (* Robert Price, May 28 2019 *)

CROSSREFS

Cf. A091120, A091122, A091123, A091124, A091125.

Sequence in context: A394580 A331796 A193221 * A026005 A386959 A398639

Adjacent sequences: A091118 A091119 A091120 * A091122 A091123 A091124

KEYWORD

nonn,more

AUTHOR

Eric W. Weisstein, Dec 19 2003

EXTENSIONS

a(10) from Robert G. Wilson v, Dec 22 2003

a(11)-a(14) from Hiroaki Yamanouchi, Oct 14 2014

a(15)-a(19) from Benjamin Chaffin, Jun 02 2026

a(19) corrected by Benjamin Chaffin, Jul 08 2026

STATUS

approved