|
|
A077798
|
|
Palindromic wing primes (a.k.a. near-repdigit palindromic primes) of the general form r*(10^d - 1)/9 + (m-r)*10^floor(d/2) where d is the number of digits (an odd number > 1), r is the repeated digit, and m (different from r) is the middle digit.
|
|
48
|
|
|
101, 131, 151, 181, 191, 313, 353, 373, 383, 727, 757, 787, 797, 919, 929, 11311, 11411, 33533, 77377, 77477, 77977, 1114111, 1117111, 3331333, 3337333, 7772777, 7774777, 7778777, 111181111, 111191111, 777767777, 77777677777, 99999199999, 1111118111111
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
Prime versus probable prime status and proofs are given in the author's table.
|
|
REFERENCES
|
C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 28, No. 1, 1996-97, pp. 1-9.
|
|
LINKS
|
|
|
PROG
|
(Magma) a:=[]; for d in [3..13 by 2] do for r in [1..9] do for m in [0..9] do if m ne r then t:=r*((10^d-1) div 9) + (m-r)*10^(d div 2); if IsPrime(t) then a[#a+1]:=t; end if; end if; end for; end for; end for; a; // Jon E. Schoenfield, Nov 04 2018
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,base
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|