OFFSET
1,1
COMMENTS
Prime digits are 2, 3, 5 or 7.
FORMULA
a(n) ~ 2.5n
CROSSREFS
KEYWORD
nonn,base,less
AUTHOR
Juri-Stepan Gerasimov, Mar 13 2009
EXTENSIONS
Entries checked by R. J. Mathar, May 19 2010
STATUS
approved