A097446 Concatenate consecutive prime-sided isosceles triangles.

233, 355, 577, 71111, 111313, 131717, 171919, 192323, 232929, 293131, 313737, 374141, 414343, 434747, 475353, 535959, 596161, 616767, 677171, 717373, 737979, 798383, 838989, 899797, 97101101, 101103103, 103107107, 107109109, 109113113

Offset

2,1

Links

Table of n, a(n) for n=2..30.

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 for output.

Example

For side x = 7, y = 11 to get concatenate 71111.

Mathematica

con[a_, b_]:=FromDigits[Join[IntegerDigits[a], IntegerDigits[b], IntegerDigits[ b]]]; con@@@Partition[Prime[Range[50]], 2, 1] (* Harvey P. Dale, Jul 25 2011 *)

Prog

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

Crossrefs

Sequence in context: A160574 A087862 A141280 * A154621 A243891 A142644

Adjacent sequences: A097443 A097444 A097445 * A097447 A097448 A097449

Keyword

nonn,base

Author

Cino Hilliard, Aug 23 2004

Status

approved