A108388 Transmutable primes: Primes with distinct digits d_i, i=1,m (2<=m<=4) such that simultaneously exchanging all occurrences of any one pair (d_i,d_j), i<>j results in a prime.
13, 17, 31, 37, 71, 73, 79, 97, 113, 131, 179, 191, 199, 313, 331, 337, 773, 911, 919, 1171, 1933, 3391, 7717, 9311, 11113, 11119, 11177, 11717, 11933, 33199, 33331, 77171, 77711, 77713, 79999, 97777, 99991, 113111, 131111, 131113, 131171, 131311
Offset: 1
Examples
179 is a term because it is prime and its three transmutations are all prime: exchanging ('transmuting') 1 and 7: 179 ==> 719 (prime), exchanging 1 and 9: 179 ==> 971 (prime) and exchanging 7 and 9: 179 ==> 197 (prime). (As 791 and 917 are not prime, 179 is not a term of A068652 or A003459 also.). Similarly, 1317713 is transmutable: exchanging all 1's and 3s: 1317713 ==> 3137731 (prime), exchanging all 1's and 7s: 1317713 ==> 7371173 (prime) and exchanging all 3s and 7s: 1317713 ==> 1713317 (prime).
Links
- Michael S. Branicky, Table of n, a(n) for n = 1..10000
Crossrefs
Cf. A108382, A108383, A108384, A108385, A108386, A108389 (transmutable primes with four distinct digits), A083983 (transmutable primes with two distinct digits), A108387 (doubly-transmutable primes), A006567 (reversible primes), A002385 (palindromic primes), A068652 (every cyclic permutation is prime), A003459 (absolute primes).
Programs
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Python
from gmpy2 import is_prime from itertools import combinations, count, islice, product def agen(): # generator of terms for d in count(2): for p in product("1379", repeat=d): p, s = "".join(p), sorted(set(p)) if len(s) == 1: continue if is_prime(t:=int(p)): if all(is_prime(int(p.translate({ord(c):ord(d), ord(d):ord(c)}))) for c, d in combinations(s, 2)): yield t print(list(islice(agen(), 50))) # Michael S. Branicky, Dec 15 2023
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