formula - Equation of 1 22 333 4444 55555 sequence? -

i need find 1 22 333 sequence formula/equation.

i write code getting number need find equation of sequence

code:

for (int = 1; <= 9; i++) {     (int j = 0; j < i; j++)     {         console.write(i);     }      console.write("\n"); }

with code results

1 22 333 4444 55555 666666 7777777 88888888 999999999

also latex code line should works me to.

i mean equation somethings example:

example equation

from sum of geometric progression, value of (n)th term is

n*(power(10, n) - 1)/9

where power(a, b) raises a bth power.

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