A052089 Primes formed by concatenating k with k-1.

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

Links

Paul Tek, Table of n, a(n) for n = 1..10000

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

Cf. A030458, A052087, A052088.

Sequence in context: A142055 A052088 A068699 * A260809 A039471 A104783

Adjacent sequences: A052086 A052087 A052088 * A052090 A052091 A052092

Keyword

nonn,base

Author

Patrick De Geest, Jan 15 2000

Status

approved