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

Author

Cino Hilliard, Jun 21 2004

Keywords

• base
• easy
• nonn

Comments

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

Examples

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

Links

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

Crossrefs

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

Programs

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 *)

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

Extensions

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