A130174 a(n) = n-1 + (total number of digits in a(1), ..., a(n-1)).

0, 2, 4, 6, 8, 10, 13, 16, 19, 22, 25, 28, 31, 34, 37, 40, 43, 46, 49, 52, 55, 58, 61, 64, 67, 70, 73, 76, 79, 82, 85, 88, 91, 94, 97, 100, 104, 108, 112, 116, 120, 124, 128, 132, 136, 140, 144, 148, 152, 156, 160, 164, 168, 172, 176, 180, 184, 188, 192, 196, 200, 204

Offset

1,2

Links

Alois P. Heinz, Table of n, a(n) for n = 1..32768

Formula

a(n) = n - 1 + Sum_{i=1..n-1} A055642(a(i)).

a(n) = a(n-1) + 1 + A055642(a(n-1)) for n>1.

Example

0,2,4,6,8,10,13,16: next term is 19 because there are so far 8 integers in the sequence and 11 digits; and 8+11=19.

Maple

s:= proc(n) option remember; `if`(n<2, n, s(n-1)+length(a(n))) end:
a:= proc(n) option remember; n-1+s(n-1) end:
seq(a(n), n=1..62);  # Alois P. Heinz, Feb 06 2025

Mathematica

s={0}; Do[AppendTo[s, n-1+Length[Flatten[IntegerDigits/@s]]], {n, 2, 62}]; s (* James C. McMahon, Feb 06 2025 *)

Crossrefs

Cf. A055642.

Sequence in context: A371186 A053044 A129011 * A061168 A130798 A165453

Adjacent sequences: A130171 A130172 A130173 * A130175 A130176 A130177

Keyword

base,easy,nonn

Author

Eric Angelini, Aug 05 2007

Status

approved