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%I #27 Feb 13 2024 14:34:34
%S 2,3,2,3,2,5,2,3,2,3,13,5,3,13,2,3,2,5,23,3,2,23,3,5,29,3,2,3,31,29,2,
%T 7,2,37,37,5,41,37,41,3,5,13,47,43,2,5,53,7,53,7,2,3,59,17,59,3,5,59,
%U 61,11,67,5,2,7,2,67,5,3,71,13,7,5,2,73,79,37,79,5,83,3,83,3,5,11,2
%N Smallest prime p such that n is a palindrome in base-p representation.
%C A016026(n) <= a(n) <= A007918(n).
%o (Python)
%o from sympy import sieve
%o from sympy.ntheory import is_palindromic
%o def a086757(n): return next(p for p in sieve if is_palindromic(n, p)) # _Dumitru Damian_, Jan 29 2024
%o (PARI) isok(p,n) = my(d=digits(n,p)); d == Vecrev(d);
%o a(n) = my(p=2); while (!isok(p,n), p=nextprime(p+1)); p; \\ _Michel Marcus_, Jan 30 2024
%Y Cf. A007918, A016026.
%Y Cf. A006995 (a(n)=2).
%K nonn,base
%O 1,1
%A _Reinhard Zumkeller_, Aug 01 2003
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