21111: Near Repdigit 211..11

First few terms (base 10): \[[21^*_5]_n=\{2,11,56,281,1406,\ldots\}\]

First few terms (base 5): \[\{\text{2},\text{21},\text{211},\text{2111},\text{21111},\ldots\}\]

General Formula:\[[21^*_5]_n={9\cdot5^{n}-1\over4}\]

Equivalent Patterns: \[[42^*_5]_n=2\cdot[21^*_5]_n\]

Table

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