A068188 Tetradic primes (primes in A006072).

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

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: A061247 A199328 A370447 * 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