|
|
A075240
|
|
Smallest prime whose base-n reversal is not a prime.
|
|
2
|
|
|
2, 3, 11, 5, 13, 7, 11, 29, 19, 11, 19, 13, 29, 23, 19, 17, 23, 19, 31, 29, 29, 23, 29, 37, 37, 29, 31, 29, 43, 31, 37, 37, 59, 59, 43, 37, 41, 59, 43, 41, 59, 43, 47, 47, 53, 47, 59, 61, 59, 61, 59, 53, 67, 59, 59, 59, 61, 59, 73, 61, 71, 67, 79, 71, 89, 67, 71, 101, 89
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
2,1
|
|
COMMENTS
|
All primes show up in the sequence eventually.
|
|
LINKS
|
|
|
EXAMPLE
|
11_10 = 23_4, reverse(23) = 32, 32_4 = 14_10, so a(4) = 11 since this does not work for smaller primes.
|
|
MATHEMATICA
|
a = {}; Do[k = 1; While[ PrimeQ[ FromDigits[ Reverse[ IntegerDigits[ Prime[k], n]], n]], k++ ]; a = Append[a, Prime[k]], {n, 2, 70}]; a
|
|
PROG
|
(PARI) a(n) = my(p=2); while (isprime(fromdigits(Vecrev(digits(p, n)), n)), p = nextprime(p+1)); p; \\ Michel Marcus, Mar 28 2021
|
|
CROSSREFS
|
|
|
KEYWORD
|
base,easy,nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|