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%I #30 Dec 17 2017 22:14:41
%S 11,101,181,18181,1008001,1180811,1880881,1881881,100111001,100888001,
%T 108101801,110111011,111010111,111181111,118818811,180101081,
%U 181111181,181888181,188010881,188888881,10008180001,10081818001
%N Tetradic primes (primes in A006072).
%C Primes that are palindromes and use only the digits 0, 1 and 8, so they read the same backwards and upside down.
%C 11 is the only term with an even number of digits. The number of terms for an odd number of digits (3-37) is: 2, 1, 4, 12, 26, 62, 173, 392, 1087, 3197, 8189, 23354, 65128, 181486, 514255, 1447637, 4052813, 11682721. That makes the number of terms less than 10^2n (n to 19): 1, 3, 4, 8, 20, 46, 108, 281, 673, 1760, 4957, 13146, 36500, 101628, 283114, 797369, 2245006, 6297819, 17980540. - _Hans Havermann_, Dec 16 2017
%H Hans Havermann, <a href="/A068188/b068188.txt">Table of n, a(n) for n = 1..36500</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/TetradicNumber.html">Tetradic Number</a>
%t TetrPrmsUpTo10powerK[k_]:= Select[FromDigits/@ Tuples[{0,1,8}, k],
%t PrimeQ[#] && IntegerDigits[#] == Reverse[IntegerDigits[#]] &]; TetrPrmsUpTo10powerK[13] (* _Mikk Heidemaa_, May 20 2017 *)
%Y Cf. A006072, subsequence of A030430.
%K nonn,easy,base
%O 1,1
%A _Eric W. Weisstein_, Feb 18 2002
%E Edited by _Jud McCranie_, Jun 02 2003
%E Offset corrected by _Arkadiusz Wesolowski_, Oct 17 2011
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