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A069706
Primes with property that swapping first and last digits also gives a prime.
6
2, 3, 5, 7, 11, 13, 17, 31, 37, 71, 73, 79, 97, 101, 107, 113, 131, 149, 151, 157, 167, 179, 181, 191, 199, 311, 313, 337, 347, 353, 359, 373, 383, 389, 701, 709, 727, 733, 739, 743, 751, 757, 761, 769, 787, 797, 907, 919, 929, 937, 941, 953, 967, 971, 983, 991, 1009, 1013
OFFSET
1,1
COMMENTS
This is not the same as A007500, "palindromic" primes.
EXAMPLE
1049 and 9041 both are primes hence both are members.
MAPLE
swapdigs:= proc(n) local d;
d:= ilog10(n);
n + ((n mod 10)-floor(n/10^d))*(10^d-1);
end proc:
select(isprime and isprime @ swapdigs, [2, seq(2*i+1, i=1..10^4)]); # Robert Israel, Nov 11 2015
MATHEMATICA
Do[t = IntegerDigits[ Prime[n]]; u = t; u[[1]] = t[[ -1]]; u[[ -1]] = t[[1]]; t = FromDigits[u]; If[ PrimeQ[t], Print[ Prime[n]]], {n, 1, 300}]
PROG
(Python)
from sympy import prime, isprime
A069706_list = [2, 3, 5, 7]
for i in range(5, 10**6):
p = prime(i)
s = str(p)
if isprime(int(s[-1]+s[1:-1]+s[0])):
A069706_list.append(p) # Chai Wah Wu, Nov 11 2015
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Amarnath Murthy, Apr 08 2002
EXTENSIONS
Edited and extended by Robert G. Wilson v, Apr 12 2002
Edited by N. J. A. Sloane, Jan 20 2009
STATUS
approved