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Numbers k for which there exist k-digit palindromic wing primes (a.k.a. near-repdigit palindromic primes) of the general form r*(10^k - 1)/9 + (m-r)*10^floor(k/2) where k is the number of digits (an odd number > 1), r is the repeated digit, and m (different from r) is the middle digit.
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%I #15 Aug 11 2024 14:41:34

%S 3,5,7,9,11,13,15,17,19,21,23,25,27,29,35,39,41,45,47,53,59,63,65,67,

%T 73,79,81,87,91,109,117,119,123,139,155,159,171,177,181,185,189,195,

%U 209,225,231,233,237,259,321,325,337,339,355,363,371,375,397,425,453

%N Numbers k for which there exist k-digit palindromic wing primes (a.k.a. near-repdigit palindromic primes) of the general form r*(10^k - 1)/9 + (m-r)*10^floor(k/2) where k is the number of digits (an odd number > 1), r is the repeated digit, and m (different from r) is the middle digit.

%D C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 28, No. 1, 1996-97, pp. 1-9.

%H P. De Geest, <a href="https://www.worldofnumbers.com/pwpsorted.htm">PWP's Sorted By Length</a>

%Y Cf. A077775-A077798.

%K nonn,base

%O 1,1

%A _Patrick De Geest_, Nov 16 2002

%E Name edited by _Jon E. Schoenfield_, Nov 04 2018