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A055558 Primes of form 1999...999. 8
19, 199, 1999, 199999, 19999999, 199999999999999999999999999, 1999999999999999999999999999, 199999999999999999999999999999999999999999999999999999 (list; graph; refs; listen; history; internal format)
OFFSET

1,1

FORMULA

a(n)=2*10^n-1 and is prime

EXAMPLE

2*10^n-1 is prime for {1,2,3,5,7,26,27,53,147,236,248,386,401} n gives how many digit 9 occurs in these numbers

CROSSREFS

A051200.

Sequence in context: A067272 A037071 A065582 * A160452 A113596 A155670

Adjacent sequences:  A055555 A055556 A055557 * A055559 A055560 A055561

KEYWORD

base,nonn

AUTHOR

Labos E. (labos(AT)ana.sote.hu), Jul 10 2000

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Last modified February 14 08:19 EST 2012. Contains 205609 sequences.