A104759 Concatenation of digits of natural numbers from n down to 1.

1, 21, 321, 4321, 54321, 654321, 7654321, 87654321, 987654321, 1987654321, 1987654321, 101987654321, 1101987654321, 11101987654321, 211101987654321, 1211101987654321, 31211101987654321, 131211101987654321

Offset

1,2

Links

Michael De Vlieger, Table of n, a(n) for n = 1..1000 (last term has 1000 decimal digits)

Eric Weisstein's World of Mathematics, Consecutive numbers sequences.

Formula

a(n) = A138793(n) mod 10^(n-1). - R. J. Mathar, Sep 17 2011

Example

a(11) = a(10) because no number may begin with 0.
a(9)= [123456789]101112131415...=987654321
a(10)=[1234567891]01112131415...=1987654321
a(11)=[12345678910]1112131415...=01987654321=1987654321
a(12)=[123456789101]112131415...=101987654321
a(13)=[1234567891011]12131415...=1101987654321
a(14)=[12345678910111]2131415...=11101987654321
a(15)=[123456789101112]131415...=211101987654321

Mathematica

f[n_] := Block[{t = Reverse@ Flatten@ IntegerDigits@ Range@ n, k}, Reap@ For[k = 1, k <= Length@ t, k++, Sow[FromDigits@ Take[t, -k]]] // Flatten // Rest]; f@ 14 (* Michael De Vlieger, Mar 23 2015 *)
lst = {}; Do[lst = Join[lst, IntegerDigits[n]], {n, 1, 100}]; Table[FromDigits[Reverse[lst[[Range[1, n]]]]], {n, 1, Length[lst]}] (* Robert Price, Mar 24 2015 *)

Crossrefs

Cf. A014925, A000422, A057138, A060554...

Sequence in context: A069572 A260487 A057138 * A138793 A014925 A000422

Adjacent sequences: A104756 A104757 A104758 * A104760 A104761 A104762

Keyword

easy,nonn,base

Author

Alexandre Wajnberg & Juliette Bruyndonckx, Apr 23 2005

Status

approved