OFFSET
0,2
COMMENTS
Up to n=8 the digits of a(n) sum up to n^2.
Similar to this, A014824 (1,12,123,1234,...) is a representation of the triangular numbers; (1,1112,1112223,1112223334,...) of the pentagonal numbers;(1,11112,111122223,...) of the hexagonal numbers, and so on. A nice thing about this sequence(s) is that the (represented) value of the integer matches the partial sums of the number of digits in the sequence.
FORMULA
a(n) = Sum_{k=0..n} A100706(k). - Michel Marcus, Mar 12 2023
PROG
(PARI) A100706(n) = (10^(2*n + 1) - 1)/9;
a(n) = sum(k=0, n, A100706(k)); \\ Michel Marcus, Mar 12 2023
CROSSREFS
KEYWORD
nonn
AUTHOR
Mark Dols, Aug 07 2010
EXTENSIONS
More terms and edited by Michel Marcus, Mar 12 2023
STATUS
approved