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A052089
Primes formed by concatenating k with k-1.
32
43, 109, 2221, 2423, 3433, 4241, 5857, 7069, 7877, 8887, 10099, 102101, 108107, 112111, 114113, 124123, 148147, 154153, 160159, 172171, 180179, 192191, 198197, 202201, 208207, 210209, 214213, 238237, 244243, 262261, 264263, 268267, 270269, 282281, 294293, 300299
OFFSET
1,1
EXAMPLE
2423 is a prime and a concatenation of 24 and 23.
MATHEMATICA
Sort[Select[FromDigits[Flatten[IntegerDigits/@#]]&/@Partition[ Range[ 300, 1, -1], 2, 1], PrimeQ]] (* Harvey P. Dale, May 09 2012 *)
PROG
(PARI) for(n=4, 1e4, if(isprime(t=eval(Str(n, n-1))), print1(t", "))) \\ Charles R Greathouse IV, May 07 2013
(Magma) [Seqint(Intseq(n-1) cat Intseq(n)): n in [2..300 by 2] | IsPrime(Seqint(Intseq(n-1) cat Intseq(n)))]; // Marius A. Burtea, Mar 21 2019
(Python)
from sympy import isprime
from itertools import count, islice
def agen(): yield from filter(isprime, (int(str(k)+str(k-1)) for k in count(2, 2)))
print(list(islice(agen(), 36))) # Michael S. Branicky, Aug 05 2022
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Patrick De Geest, Jan 15 2000
STATUS
approved