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[ 31113 in anupward (2<=b<=10) and downward (10>=b>=2) string produces two genuine primes.Prime 1 = 3111346610746111564654000131443423132120211120200100111100110001001 Prime 2 = 1111001100010011120200100132120211443423400013156465746114661031113 The following palindrome with this property is So, who can provide me the first palindromic prime example ?
\\ Patrick De Geest [ GP/PARI CALCULATOR Version 2.11.4 ] February 7, 2022 { forstep(a=1,oo,2, t=digits(a); if(Vecrev(t)==t, spup=[]; spdo=[]; marque=0; for(i=2,10, spup=concat(spup,digits(a,i)); spdo=concat(digits(a,i),spdo) ); if(isprime(fromdigits(spup)) && isprime(fromdigits(spdo)), marque=1; print(fromdigits(spdo));print(fromdigits(spup));print()); if(isprime(a)&&marque, print(a," is a palindromic PRIME!"); break()); ); ); }
On [
98802520889 Prime 1 = 98802520889313021332645134010555147110065263366522 \ Prime 2 = 1011100000001000101101101001100111001100110000201101002201112 \ Note that the primes formed by the concatenations Direct OEIS ReferencesConcatenation of n in base 2 up to base 10 and n in base 10 down to base 2 is prime, all numbers are interpreted as decimals. A054257 Concatenation of n in base 10 down up to base 2 is prime, all numbers are interpreted as decimals. A054256 Concatenation of n in base 2 up to base 10 is prime, all numbers are interpreted as decimals. Indirect OEIS ReferencesConcatenation of n in base 10 down to base 2 is divisible by at least one of these base b numbers, all numbers interpreted as decimals. A054220 Concatenation of n in base 2 up to base 10 is divisible by at least one of these base b numbers, all numbers interpreted as decimals. | |||

A000071 Prime Curios! Prime Puzzle Wikipedia 71 Le Nombre 71 Numberland 71 |

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