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%I #12 Jun 28 2022 15:27:51
%S 7,97,991,9967,99989,999983,9999971,99999827,999999893,9999999967,
%T 99999999977,999999999959,9999999999799,99999999999959,
%U 999999999999877,9999999999999571,99999999999997997,999999999999999737,9999999999999999719,99999999999999999631
%N Largest n-digit prime whose digit reversal is also prime.
%H Michael S. Branicky, <a href="/A114019/b114019.txt">Table of n, a(n) for n = 1..527</a>
%t f[n_] := Block[{k = 10^n}, While[ !PrimeQ[k] || !PrimeQ[FromDigits@Reverse@IntegerDigits@k], k-- ]; k]; Array[f, 19] (* _Robert G. Wilson v_, Nov 19 2005 *)
%o (Python)
%o from sympy import isprime
%o def c(n): return isprime(n) and isprime(int(str(n)[::-1]))
%o def a(n): return next(p for p in range(10**n-1, 10**(n-1), -2) if c(p))
%o print([a(n) for n in range(1, 21)]) # _Michael S. Branicky_, Jun 27 2022
%Y Cf. A113018.
%K base,nonn
%O 1,1
%A _Amarnath Murthy_, Nov 12 2005
%E More terms from _Robert G. Wilson v_, Nov 19 2005
%E a(19) and beyond from _Michael S. Branicky_, Jun 27 2022
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