A300400 - OEIS

%I #25 Mar 27 2018 05:54:56

%S 2,24,246,2491,25009,249940,2499751,25000026,249997694,2499999305,

%T 24999974939,249999962302

%N a(n) = number of primes that end in 9 among the first 10^n primes.

%H Caldwell and Honaker, <a href="https://primes.utm.edu/curios/page.php/2499751.html">Prime Curios!</a>

%F a(n) = A185715(A006988(n)). - _Michel Marcus_, Mar 20 2018

%e a(1) = 2 because the first 10 primes are 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, among which there are two primes ending in 9.

%o (PARI) a(n) = #select(x->((x % 10) == 9), primes(10^n)); \\ _Michel Marcus_, Mar 07 2018

%Y Cf. A006988, A030433, A185715, A300397, A300398, A300399.

%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