OFFSET

1,1

COMMENTS

Appears to be the union of the perfect squares k^2 (for k>1) and the prime powers p^k (for k>1) with some exceptions, such as 2^3, 3^3, 2^7, etc.

The perfect powers except those of the form n^(p^m) where p and (n^(p^(m+1))-1)/(n^(p^m)-1) are primes, p>2 and m>=1. - Max Alekseyev, Mar 09 2009

LINKS

H. Dubner, Generalized repunit primes, Math. Comp., 61 (1993), 927-930.

Eric Weisstein's World of Mathematics, Repunit.

EXAMPLE

A128164 begins with offset 2: {3, 3, 0, 3, 3, 5, 3, 0, 19, 17, 3, 5, 3, 3, 0, 3, ...}. Thus a(1) = 4, a(2) = 9, a(3) = 16.

CROSSREFS

KEYWORD

nonn

AUTHOR

Alexander Adamchuk, Mar 13 2007

EXTENSIONS

Extended by Max Alekseyev, Mar 09 2009

STATUS

approved