0,1

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.

For the first entry n=2 the formula produces the prime 151.

(PARI) /* n=number of values to test, r=repeat digits, eg., 14, 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", ")))

Sequence in context: A096367 A058738 A095376 this_sequence A144657 A167555 A109869

Adjacent sequences: A153329 A153330 A153331 this_sequence A153333 A153334 A153335

nonn

Cino hilliard (hillcino368(AT)hotmail.com), Dec 23 2008