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 A068188 Tetradic primes (primes in A006072). 6
 11, 101, 181, 18181, 1008001, 1180811, 1880881, 1881881, 100111001, 100888001, 108101801, 110111011, 111010111, 111181111, 118818811, 180101081, 181111181, 181888181, 188010881, 188888881, 10008180001, 10081818001 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Primes that are palindromes and use only the digits 0, 1 and 8, so they read the same backwards and upside down. 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 LINKS Hans Havermann, Table of n, a(n) for n = 1..36500 Eric Weisstein's World of Mathematics, Tetradic Number MATHEMATICA TetrPrmsUpTo10powerK[k_]:= Select[FromDigits/@ Tuples[{0, 1, 8}, k], PrimeQ[#] && IntegerDigits[#] == Reverse[IntegerDigits[#]] &]; TetrPrmsUpTo10powerK[13] (* Mikk Heidemaa, May 20 2017 *) CROSSREFS Cf. A006072, subsequence of A030430. Sequence in context: A007597 A061247 A199328 * A032592 A180404 A142317 Adjacent sequences: A068185 A068186 A068187 * A068189 A068190 A068191 KEYWORD nonn,easy,base AUTHOR Eric W. Weisstein, Feb 18 2002 EXTENSIONS Edited by Jud McCranie, Jun 02 2003 Offset corrected by Arkadiusz Wesolowski, Oct 17 2011 STATUS approved

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Last modified October 4 10:09 EDT 2023. Contains 365874 sequences. (Running on oeis4.)