21111: Near Repdigit 211..11

First few terms (base 10): \[[21^*_9]_n=\{2,19,172,1549,13942,\ldots\}\]

First few terms (base 9): \[\{\text{2},\text{21},\text{211},\text{2111},\text{21111},\ldots\}\]

General Formula:\[[21^*_9]_n={17\cdot9^{n}-1\over8}\]

Equivalent Patterns: \[[42^*_9]_n=2\cdot[21^*_9]_n\] \[[84^*_9]_n=4\cdot[21^*_9]_n\] \[[63^*_9]_n=3\cdot[21^*_9]_n\]

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