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a(n) = number of primes that end in 3 among the first 10^n primes.
3

%I #27 Apr 03 2023 10:36:13

%S 3,26,253,2515,25007,250110,2500209,25000135,250002220,2500000243,

%T 25000027724,250000009260

%N a(n) = number of primes that end in 3 among the first 10^n primes.

%H Caldwell and Honaker, <a href="https://t5k.org/curios/page.php?curio_id=31995">Prime Curios!</a>

%F a(n) = A185712(A006988(n)). - _Michel Marcus_, Mar 20 2018

%e a(1) = 3 because the first 10 primes are 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, among which there are three primes ending in 3.

%o (PARI) a(n) = #select(x->((x % 10) == 3), primes(10^n)); \\ _Michel Marcus_, Mar 07 2018

%Y Cf. A006988, A030431, A185712, A300397, A300399, A300400.

%K nonn,base,more

%O 1,1

%A _G. L. Honaker, Jr._, Mar 05 2018

%E a(3)-a(8) from Chuck Gaydos

%E a(9) from _Jon E. Schoenfield_, Mar 20 2018

%E a(10)-a(12) from _Giovanni Resta_, Mar 27 2018

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Last modified September 21 10:45 EDT 2024. Contains 376084 sequences. (Running on oeis4.)