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%I #22 Mar 25 2021 03:39:35
%S 1,1,3,3,6,6,18,18,26,26,73,73,179,179,459,459,1179,1179,3004,3004,
%T 8111,8111,22183,22183,60789,60789,168641,168641,469689,469689,
%U 1322664,1322664,3691761,3691761,10390938,10390938,29502559,29502559,84012658,84012658,239417332,239417332
%N Total number of palindromic primes in base 3 below 3^n.
%C Every palindrome with an even number of digits is divisible by 11 (in base 3) and therefore is composite (not prime). Hence there is no palindromic prime with an even number of digits.
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/PalindromicPrime.html">Palindromic Prime</a>.
%F a(2*k-1) = a(2*k) for k >= 1. - _Bernard Schott_, Mar 23 2021
%e a(5) = a(6) = 6 as the six palindromic primes below 3^5 are 2_10 = 2_3, 13_10 = 111_3, 23_10 = 212_3, 151_10 = 12121_3, 173_10 = 20102_3, 233_10 = 22122_3. There are no palindromic primes with 6 digits so a(5) = a(6). - _David A. Corneth_, Mar 21 2021
%Y Partial sums of A117776.
%Y Cf. A029971, A117698.
%Y Cf. A117772, A117777, A117779, A117781, A117783, A117785, A117787.
%K nonn,base
%O 1,3
%A _Martin Renner_, Apr 15 2006
%E a(15)-a(42) from the data at A117776 added by _Amiram Eldar_, Mar 21 2021
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