cp's OEIS Frontend

A077353 a(n) = (concatenation in ascending order of divisors of 5^n)/5^n.

%I A077353 #26 May 19 2025 15:59:30
%S A077353 1,3,61,12201,2440201,4880402001,97608040020001,1952160800400020001,
%T A077353 390432160080004000200001,780864320160008000400002000001,
%U A077353 1561728640320016000800004000002000001,31234572806400320016000080000040000020000001,6246914561280064003200016000008000004000000200000001
%N A077353 a(n) = (concatenation in ascending order of divisors of 5^n)/5^n.
%H A077353 Paolo Xausa, <a href="/A077353/b077353.txt">Table of n, a(n) for n = 0..50</a>
%F A077353 a(0) = 1, a(n) = (10^A055642(5^n)/5)*a(n-1) + 1. - _Jason Yuen_, Aug 21 2024
%e A077353 a(5) = 15251256253125/3125 = 4880402001.
%p A077353 a:= n-> parse(cat(5^i$i=0..n))/5^n:
%p A077353 seq(a(n), n=0..12);  # _Alois P. Heinz_, May 16 2025
%t A077353 A077353[n_] := FromDigits[Flatten[IntegerDigits[Divisors[#]]]]/# & [5^n];
%t A077353 Array[A077353, 16, 0] (* or *)
%t A077353 FoldList[10^IntegerLength[5^#2]/5*# + 1 &, 1, Range[15]] (* _Paolo Xausa_, May 19 2025 *)
%o A077353 (PARI) a(n) = eval(concat(apply(x->Str(x),divisors(5^n))))/5^n \\ _Max Alekseyev_, Dec 12 2011
%o A077353 (PARI) a(n) = if(n==0,1,(10^#Str(5^n)/5)*a(n-1)+1) \\ _Jason Yuen_, Aug 21 2024
%Y A077353 Cf. A000351, A055642, A077351, A069872, A077352.
%K A077353 base,nonn,easy
%O A077353 0,2
%A A077353 _Amarnath Murthy_, Nov 05 2002
%E A077353 More terms from _Max Alekseyev_, Dec 12 2011