OFFSET
0,2
COMMENTS
Number of integers from 0 to (10^n)-1 that lack 0, 1, 2 and 3 as a digit.
Also, a(n) is the expected number of tosses of a single die needed to obtain for the first time a string of n consecutive 6's. - Jean M. Morales, Aug 04 2012
LINKS
FORMULA
a(n) = 6^n+a(n-1) (with a(0)=0). - Vincenzo Librandi, Nov 13 2010
a(n) = 7*a(n-1)-6*a(n-2). G.f.: 6*x/((x-1)*(6*x-1)). - Colin Barker, Jan 28 2013
MAPLE
a:=n->add(6^j, j=1..n): seq(a(n), n=0..30); # Zerinvary Lajos, Oct 03 2007
MATHEMATICA
NestList[6#+6&, 0, 30] (* Harvey P. Dale, Jul 24 2012 *)
PROG
(PARI) a(n)=if(n<0, 0, (6^n-1)*6/5)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Alexandre Wajnberg, Apr 25 2005
EXTENSIONS
More terms from Harvey P. Dale, Jul 24 2012
STATUS
approved