This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A153333 Numbers n such that (10^n-1)*160/99+1 is prime. 0
 6, 54, 108, 144, 228, 960 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS These numbers are always even. If n is odd, then 10^n-1 produces a number with an odd number of 9's which 99 does not divide. Also the numbers produced by this formula are palindromic. LINKS EXAMPLE For the first entry n=6, the formula produces the prime 1616161. PROG (PARI) /* n=number of values to test, r=repeat digits, eg., 16, 121, 177, 1234, etc. d = last digit appended to the end */ repr(n, r, d) = ln=length(Str(r)); for(x=0, n, y=(10^(ln*x)-1)*10*r/(10^ln-1)+1; if(ispseudoprime(y), print1(ln*x", "))) CROSSREFS Sequence in context: A221413 A145003 A097645 * A195901 A072368 A116138 Adjacent sequences:  A153330 A153331 A153332 * A153334 A153335 A153336 KEYWORD nonn AUTHOR Cino hilliard (hillcino368(AT)hotmail.com), Dec 23 2008 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Transforms | Puzzles | Hot | Classics
Recent Additions | More pages | Superseeker | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement .