A342943 Primes whose palindromization is a prime.

13, 19, 31, 37, 79, 103, 113, 127, 139, 163, 179, 181, 193, 199, 307, 353, 719, 727, 773, 787, 907, 937, 967, 983, 1093, 1117, 1123, 1129, 1153, 1163, 1193, 1201, 1303, 1327, 1409, 1447, 1489, 1579, 1583, 1597, 1609, 1657, 1777, 1823, 1831, 1879, 1951, 1987, 1993, 3001

Offset

1,1

Comments

Palindromization is the function that extends the string representation of a number into a palindrome.

Even palindromization is the concatenation of a number and its reversal. Odd palindromization excludes the first digit of the reversal.

Links

Michel Marcus, Table of n, a(n) for n = 1..11962

Mathematica

Select[Prime@Range[5, 500], Or@@(PrimeQ/@FromDigits/@(Join[a, Reverse@#]&/@{a=IntegerDigits@#, Most@a}))&] (* Giorgos Kalogeropoulos, Mar 30 2021 *)
plndrQ[n_]:=Module[{a=n 10^IntegerLength[n]+IntegerReverse[n], b=n 10^ (IntegerLength[ n]-1)+IntegerReverse[Floor[n/10]]}, AnyTrue[{a, b}, PrimeQ]]; Select[Prime[Range[5, 500]], plndrQ] (* Harvey P. Dale, Nov 20 2022 *)

Prog

(PARI) rev(x) = strjoin(Vecrev(Str(x)));
isok(p) = isprime(p) && (isprime(eval(Str(p, rev(p)))) || isprime(eval(Str(p, rev(p\10)))));

Crossrefs

Cf. A002113, A002385.

Sequence in context: A079130 A243587 A085413 * A244311 A358530 A164333

Adjacent sequences: A342940 A342941 A342942 * A342944 A342945 A342946

Keyword

nonn,base

Author

Michel Marcus, Mar 30 2021

Status

approved