OFFSET
1,1
COMMENTS
All semiprimes of the form 7*10^n + 6 and 8*10^n + 5 are in the sequence.
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..34
Eric Weisstein's World of Mathematics, Smith Number
MATHEMATICA
e = 47; Sort[Join[{27}, 2*Select[Flatten[Union[Table[(2*10^n + 2)/2, {n, 0, e}], Table[(a*10^n + 13 - a)/2, {a, {5, 7, 9}}, {n, e}]]], PrimeQ], 5*Select[Table[(8*10^n + 5)/5, {n, e}], PrimeQ]]]
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Arkadiusz Wesolowski, Jan 14 2012
STATUS
approved