OFFSET
1,2
REFERENCES
F. Smarandache, "Properties of the numbers", Univ. of Craiova Archives, 1975; Arizona State University Special Collections, Tempe, AZ.
FORMULA
EXAMPLE
a(2) = 1 + 22 = 23 is prime.
a(6) = 1 + 22 + 333 + 4444 + 55555 + 666666 = 727021 is prime.
For what value of n is the next prime a(n)?
a(158), which has 474 digits, is prime. - Harvey P. Dale, Oct 17 2011
MATHEMATICA
Accumulate[FromDigits/@Table[Flatten[IntegerDigits/@PadLeft[{}, n, n]], {n, 15}]] (* Harvey P. Dale, Oct 17 2011 *)
CROSSREFS
KEYWORD
base,easy,nonn
AUTHOR
Jonathan Vos Post, May 11 2006
STATUS
approved