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

Author

Eric W. Weisstein, Feb 18 2002

Keywords

• nonn
• easy
• base

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

Crossrefs

Cf. A006072, subsequence of A030430.

Programs

Mathematica

TetrPrmsUpTo10powerK[k_]:= Select[FromDigits/@ Tuples[{0,1,8}, k],
PrimeQ[#] && IntegerDigits[#] == Reverse[IntegerDigits[#]] &]; TetrPrmsUpTo10powerK[13] (* Mikk Heidemaa, May 20 2017 *)

Extensions

Edited by Jud McCranie, Jun 02 2003

Offset corrected by Arkadiusz Wesolowski, Oct 17 2011