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%I #15 Jan 25 2024 12:18:48
%S 7,929,98689,9989899,999727999,99999199999,9999987899999,
%T 999999787999999,99999999299999999,9999999992999999999,
%U 999999999757999999999,99999999997579999999999
%N Largest palindromic prime with 2n-1 digits.
%C For n>1, since 11 is a proper divisor of a palindrome with 2n digits, the numbers a(n) and A028989(n+1) are consecutive in A002385. - _Jeppe Stig Nielsen_, Feb 20 2021
%H Jeppe Stig Nielsen, <a href="/A028990/b028990.txt">Table of n, a(n) for n = 1..500</a>
%H Patrick De Geest, <a href="http://www.worldofnumbers.com/palpri.htm">World!Of Palindromic Primes</a>
%o (PARI) a(n)=forstep(j=10^n-1,10^(n-1),-1,my(d=digits(j), p=fromdigits(vector(2*n-1,x,if(x<n,d[x],d[2*n-x]))));ispseudoprime(p)&&return(p));0 \\ _Jeppe Stig Nielsen_, Feb 20 2021
%Y Cf. A002385, A028989.
%K nonn,base
%O 1,1
%A _Patrick De Geest_
%E Offset changed (as it was in A028989) by _Jeppe Stig Nielsen_, Feb 20 2021
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