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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 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 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.)