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A064489
a(n) is the smallest number m such that prime(m) has prime(n) decimal digits.
2
5, 26, 1230, 78499, 455052512, 37607912019, 279238341033926, 24739954287740861, 201467286689315906291, 157589269275973410412739599
OFFSET
1,1
FORMULA
a(n) = 1 + A006880(A000040(n)-1). [Corrected by Amiram Eldar, Sep 03 2024]
a(n) = A000720(A064490(n)).
EXAMPLE
For n = 1: a(1) = 5 because prime(5) = 11 is the first prime with 2 = prime(1) decimal digits.
PROG
(PARI) l(n)=ln=0; while(n, n=floor(n/10); ln++); return(ln);
a=0; for(n=1, 10^6, x=l(prime(n)); if(isprime(x), b=x; if(b>a, a=b; print1(n, ", "))))
(Python)
from sympy import prime, nextprime, primepi
def a(n): return primepi(nextprime(10**(prime(n)-1)))
print([a(n) for n in range(1, 6)]) # Michael S. Branicky, May 26 2021
CROSSREFS
KEYWORD
base,nonn,hard,more
AUTHOR
Jason Earls, Oct 04 2001
EXTENSIONS
More terms from David Wasserman, Jul 22 2002
a(10) from the b-file at A006880 added by Amiram Eldar, Sep 03 2024
STATUS
approved