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

1, 3, 61, 12201, 2440201, 4880402001, 97608040020001, 1952160800400020001, 390432160080004000200001, 780864320160008000400002000001, 1561728640320016000800004000002000001, 31234572806400320016000080000040000020000001, 6246914561280064003200016000008000004000000200000001

Offset

0,2

Links

Paolo Xausa, Table of n, a(n) for n = 0..50

Formula

a(0) = 1, a(n) = (10^A055642(5^n)/5)*a(n-1) + 1. - Jason Yuen, Aug 21 2024

Example

a(5) = 15251256253125/3125 = 4880402001.

Maple

a:= n-> parse(cat(5^i$i=0..n))/5^n:
seq(a(n), n=0..12);  # Alois P. Heinz, May 16 2025

Mathematica

A077353[n_] := FromDigits[Flatten[IntegerDigits[Divisors[#]]]]/# & [5^n];
Array[A077353, 16, 0] (* or *)
FoldList[10^IntegerLength[5^#2]/5*# + 1 &, 1, Range[15]] (* Paolo Xausa, May 19 2025 *)

Prog

(PARI) a(n) = eval(concat(apply(x->Str(x), divisors(5^n))))/5^n \\ Max Alekseyev, Dec 12 2011
(PARI) a(n) = if(n==0, 1, (10^#Str(5^n)/5)*a(n-1)+1) \\ Jason Yuen, Aug 21 2024

Crossrefs

Cf. A000351, A055642, A077351, A069872, A077352.

Sequence in context: A173366 A125661 A386513 * A220775 A089157 A068886

Adjacent sequences: A077350 A077351 A077352 * A077354 A077355 A077356

Keyword

base,nonn,easy

Author

Amarnath Murthy, Nov 05 2002

Extensions

More terms from Max Alekseyev, Dec 12 2011

Status

approved