OFFSET
1,2
COMMENTS
Patterned-digit obtained when (1,5)-half-repdigit is divided by 15, the least such number.This simple generating rule is often[not always] applicable to provide curious digit-patterns. Thus A=1,B=7 give 111..888 numbers divided by 18 results in A003555.
FORMULA
a[n]=A*(((100^n-1)/9)+B*(10^n - 1)/9)/15, where A=1, B=5-A=4.
EXAMPLE
n = 20: a[20] = 1111111111111111111155555555555555555555/15 = 74074074074074074077037037037037037037.
MATHEMATICA
f[x_] := 3*((100^x-1)/9) + 4*(10^x-1)/9 Table[f[w], {w, 1, 20}]/15
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Oct 28 2004
STATUS
approved