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A095179
Numbers whose reversed digit representation is prime.
17
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
KEYWORD
base,easy,nonn
AUTHOR
Cino Hilliard, Jun 21 2004
EXTENSIONS
Offset corrected to 1 by Alonso del Arte, Apr 12 2020
STATUS
approved