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A048054 Number of n-digit reversible primes (emirps). 15
4, 9, 43, 204, 1499, 9538, 71142, 535578, 4197196, 33619380, 274932272, 2294771254, 19489886063 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The count includes palindromes.

LINKS

Table of n, a(n) for n=1..13.

J. L. Boal and J. H. Bevis, Permutable primes. Math. Mag., 55 (N0. 1, 1982), 38-41. [From N. J. A. Sloane, Jan 19 2012]

EXAMPLE

2, 3, 5 and 7 are 1-digit reversible primes, so a(1)=4.

MATHEMATICA

Count[Range[10^(# - 1), 10^# - 1], n_ /; And[PrimeQ@ n, PrimeQ@ FromDigits@ Reverse@ IntegerDigits@ n]] & /@ Range@ 7 (* Michael De Vlieger, Jul 14 2015 *)

PROG

(Python)

from sympy import isprime, primerange

def A048054(n):

....return len([p for p in primerange(10**(n-1), 10**n)

...........if isprime(int(str(p)[::-1]))]) # Chai Wah Wu, Aug 14 2014

CROSSREFS

Cf. A003684, A006567, A007628, A046732, A048051, A048052, A048053, A048895.

Sequence in context: A138544 A219287 A093149 * A284973 A239853 A209079

Adjacent sequences:  A048051 A048052 A048053 * A048055 A048056 A048057

KEYWORD

base,nonn,more

AUTHOR

Jud McCranie

EXTENSIONS

a(11)-a(13) from Giovanni Resta, Jul 19 2015

STATUS

approved

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Last modified January 16 03:17 EST 2019. Contains 319184 sequences. (Running on oeis4.)