A091120 - OEIS

A091120

Number of primes of the form 7k+1 less than 10^n.

0, 3, 28, 203, 1593, 13063, 110653, 960023, 8474221, 75840762, 686339040, 6267973536, 57677581458, 534156926021, 4974094941671, 46539722832425, 437259527023236, 4123325712135333, 39009611186819938

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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 + 1, {i, 0, 10^7}], PrimeQ[#] &]; Table[Count[p, x_ /; x < 10^n], {n, 7}] (* Robert Price, May 28 2019 *)

CROSSREFS

Cf. A091121, A091122, A091123, A091124, A091125.

Sequence in context: A241455 A356975 A278183 * A045737 A003466 A337590

Adjacent sequences: A091117 A091118 A091119 * A091121 A091122 A091123

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