A095179 Numbers whose reversed digit representation is prime.

2, 3, 5, 7, 11, 13, 14, 16, 17, 20, 30, 31, 32, 34, 35, 37, 38, 50, 70, 71, 73, 74, 76, 79, 91, 92, 95, 97, 98, 101, 104, 106, 107, 110, 112, 113, 118, 119, 124, 125, 128, 130, 131, 133, 134, 136, 140, 142, 145, 146, 149, 151, 152, 157, 160, 164, 166, 167, 170, 172

Offset

1,1

Comments

If m is a term, then 10*m is another term. - Bernard Schott, Nov 20 2021

Links

Michael S. Branicky, Table of n, a(n) for n = 1..11018 (all terms < 10**5)

Example

The number 70 in reverse is 07 = 7, which is prime.

Maple

q:= n-> (s-> isprime(parse(cat(s[-i]$i=1..length(s)))))(""||n):
select(q, [$1..200])[];  # Alois P. Heinz, Aug 22 2021

Mathematica

Select[Range[200], PrimeQ[FromDigits[Reverse[IntegerDigits[#]]]] &] (* Harvey P. Dale, Jun 13 2013 *)

Prog

(PARI) r(n) = for(x=1, n, y=eval(rev(x)); if(isprime(y), print1(x", "))) \ Get the reverse of the input string rev(str) = { local(tmp, j, s); tmp = Vec(Str(str)); s=""; forstep(j=length(tmp), 1, -1, s=concat(s, tmp[j])); return(s) }
(PARI) is_A095179(n)=isprime(eval(Strchr(vecextract(Vec(Vecsmall(Str(n))), "-1..1")))) \\ M. F. Hasler, Jan 13 2012
(PARI) isok(n) = isprime(fromdigits(Vecrev(digits(n)))); \\ Michel Marcus, Aug 22 2021
(Python)
from sympy import isprime
def ok(n): return isprime(int(str(n)[::-1]))
print(list(filter(ok, range(1, 173)))) # Michael S. Branicky, Aug 22 2021

Crossrefs

Cf. A004086, A007500 (primes in this sequence), A076055 (composites in this sequence), A204232 (base-2 analog), A097312.

Sequence in context: A007933 A032524 A097312 * A074895 A371653 A298536

Adjacent sequences: A095176 A095177 A095178 * A095180 A095181 A095182

Keyword

base,easy,nonn

Author

Cino Hilliard, Jun 21 2004

Extensions

Offset corrected to 1 by Alonso del Arte, Apr 12 2020

Status

approved