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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
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
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: A061247 A199328 A370447 * A032592 A180404 A142317
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