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%I #18 Aug 02 2024 12:27:36
%S 2,17,149,1069,10499,101999,1013899,10012999,100148999,1000009999,
%T 10000099999,100009799999,1000000999999,10000069999999,
%U 100001386999999,1000001939999999,10000004099999999,100000001599999999,1000000073599999999
%N Least n-digit reversible prime whose difference from its reversal is maximal.
%C Inspired by A374350.
%e Although the primes {149, 179, 199, 941, 971, 991} all have prime reversals and their differences are 792, 149 is the least. Therefore a(3) = 149.
%t a[n_] := Block[{lmt = 2*10^(n -1) +1, mx = 0, p = NextPrime[10^(n -1)], q}, While[p < lmt, q = IntegerReverse@ p; If[ PrimeQ@ q && Abs[p -q] > mx, mx = Abs[p -q]; pq = p]; p = NextPrime@ p]; pq];
%Y Cf. A374350.
%K base,nonn,more
%O 1,1
%A _Robert G. Wilson v_, Jul 06 2024