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A097447 Primes in the concatenation of consecutive prime-sided isosceles triangles. 0
233, 577, 192323, 798383, 109113113, 113127127, 127131131, 149151151, 181191191, 197199199, 223227227, 239241241, 241251251, 337347347, 431433433, 461463463, 479487487, 491499499, 641643643, 643647647, 683691691, 709719719 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Is this sequence infinite?

LINKS

Table of n, a(n) for n=1..22.

FORMULA

Consider triangles with sides (2, 3, 3), (3, 5, 5), .., (x, y, y) where x is prime and y is the next prime after x. Concatenate these sides and output if prime.

EXAMPLE

For side x = 19, y = 23 and 192323 is prime.

PROG

(PARI) f(n) = for(x=1, n, y=Str(prime(x)); y=concat(y, concat(Str(prime(x+1)), Str(prime (x+1)))); if(isprime(eval(y)), print1(y", ")))

CROSSREFS

Sequence in context: A142644 A302004 A308786 * A142783 A142848 A023338

Adjacent sequences:  A097444 A097445 A097446 * A097448 A097449 A097450

KEYWORD

nonn,base

AUTHOR

Cino Hilliard, Aug 23 2004

EXTENSIONS

Edited by Charles R Greathouse IV, Apr 29 2010

STATUS

approved

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Last modified October 17 12:25 EDT 2019. Contains 328112 sequences. (Running on oeis4.)