A097447 Primes in the concatenation of consecutive prime-sided isosceles triangles.

233, 577, 192323, 798383, 109113113, 113127127, 127131131, 149151151, 181191191, 197199199, 223227227, 239241241, 241251251, 337347347, 431433433, 461463463, 479487487, 491499499, 641643643, 643647647, 683691691, 709719719

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