OFFSET
1,1
COMMENTS
Inspired by A076449.
a(n) >= A076449(n). As an example, a(727) is 3569887, but A076449(727) is 3567889, a difference of 1998. Notice that they possess identical digits.
a(n) = A076449(n) at n = 1, 3, 4, 5, 6, 7, 8, 10, 11, 14, 18, 19, 25, 26, 29, 33, 38, 40, 45, 46, ..., .
a(n) <> A076449(n) but they have identical digits at n = 12, 13, 17, 19, 20, 21, 24, 27, 31, 32, 34, 35, 36, 37, 39, ..., .
a(n) <> A076449(n) and they do not have identical digits at n = 2, 9, 15, 16, 22, 23, 28, 30, ..., .
LINKS
David A. Corneth, Table of n, a(n) for n = 1..10000 (first 1755 terms from Robert G. Wilson v)
EXAMPLE
a(0) would be 1, but 1 is not a prime (A075053);
a(1) is 2, the first prime;
a(2) is 29 since {2 & 29} are primes but {9 & 92} are not;
a(3) is 13 since {3, 13 & 31} are primes, but 1 is not;
a(4) is 37 since all the permutations are prime, i.e.: {3, 7, 37 & 73};
a(5) is 107 since {7, 17, 71, 107 & 701} are primes; etc.
MATHEMATICA
f = Compile[{{n, _Integer}}, Floor@ Length[ Select[ Union[ FromDigits /@ Flatten[ Permutations /@ Subsets[ IntegerDigits@n], 1]], PrimeQ@# &]]]; p = 2; t[_] := 0; While[p < 114500, a = f@p; If[ t[a] == 0, t[a] = p]; p = NextPrime@ p]; t /@ Range@ 100
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Robert G. Wilson v, Mar 22 2024
STATUS
approved