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A248046 Primes p such that p^2 is the concatenation of two k-digit primes where k is half the length of p^2. 2
5, 73, 337, 409, 701, 827, 5449, 5477, 5939, 6841, 7417, 8353, 8573, 9109, 9227, 9311, 9733, 9767, 32569, 34319, 34327, 34501, 35933, 35999, 38371, 38449, 38923, 38953, 39023, 39367, 39671, 40531, 40973, 42701, 43543, 44651, 45259, 46021, 47623, 48311, 49531, 50923, 54133, 54437, 54547 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
EXAMPLE
73 is prime, and 73^2 = 5329 is the concatenation of two 2-digit primes (53 and 29). So 73 is a member of this sequence.
929 is not in the sequence since 929^2 = 863041, where 863 is a 3-digit prime but 041 is a 2-digit prime. - Jens Kruse Andersen, Oct 06 2014
PROG
(PARI)
forprime(p=1, 10^5, d=digits(p^2); if((#d)%2==0, if(isprime((p^2)\(10^(#d/2)))&&isprime((p^2)%(10^(#d/2)))&&#Str((p^2)%(10^(#d/2)))==#d/2, print1(p, ", "))))
CROSSREFS
Sequence in context: A206280 A070526 A070530 * A059017 A099667 A108444
KEYWORD
nonn,base
AUTHOR
Derek Orr, Oct 03 2014
EXTENSIONS
Terms and program corrected by Derek Orr to match definition, thanks to Jens Kruse Andersen
STATUS
approved

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Last modified February 23 11:05 EST 2024. Contains 370283 sequences. (Running on oeis4.)