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A064489 Let p = prime(n); a(n) = smallest m such that prime(m) has p digits. 2
5, 26, 1230, 78499, 455052512, 37607912019, 279238341033926, 24739954287740861, 201467286689315906291 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..9.

EXAMPLE

n=5; prime(5)=11 and 11 is the first prime with a prime number of 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; print(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

Cf. A064490.

a(n) = 1 + A006880(A000040(n-1)).

Sequence in context: A226125 A132509 A281747 * A081089 A180928 A342998

Adjacent sequences: A064486 A064487 A064488 * A064490 A064491 A064492

KEYWORD

base,easy,nonn

AUTHOR

Jason Earls, Oct 04 2001

EXTENSIONS

More terms from David Wasserman, Jul 22 2002

STATUS

approved

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Last modified January 29 00:02 EST 2023. Contains 359905 sequences. (Running on oeis4.)