%I A064108
%S A064108 1,21,421,8421,168421,3368421,67368421,1347368421,26947368421,
%T A064108 538947368421,10778947368421,215578947368421,4311578947368421,
%U A064108 86231578947368421,1724631578947368421,34492631578947368421
%N A064108 (20^n-1)/19.
%H A064108 Harry J. Smith, <a href="b064108.txt">Table of n, a(n) for n=1,...,100</
               a>
%F A064108 a(n)=20*a(n-1)+1 (with a(1)=1) [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), 
               Oct 29 2009]
%e A064108 For n=2, a(2)=20*1+1=21; n=3, a(3)=20*21+1=421: n=4, a(4)=20*421+1=8421 
               [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Oct 29 2009]
%p A064108 a:=n->sum(20^(n-j), j=0..n): seq(a(n), n=0..15); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), 
               Feb 11 2007
%o A064108 (PARI) for(n=1,23,print((20^n-1)/19))
%o A064108 (Other) sage: [gaussian_binomial(n,1,20) for n in xrange(1,17)] # [From 
               Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), May 29 2009]
%o A064108 (PARI) { for (n=1, 100, write("b064108.txt", n, " ", (20^n - 1)/19) ) 
               } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Sep 07 2009]
%Y A064108 Sequence in context: A106656 A083043 A097833 this_sequence A067895 A092499 
               A167255
%Y A064108 Adjacent sequences: A064105 A064106 A064107 this_sequence A064109 A064110 
               A064111
%K A064108 easy,nonn
%O A064108 1,2
%A A064108 Jason Earls (zevi_35711(AT)yahoo.com), Sep 17 2001