21111: Near Repdigit 211..11

First few terms (base 10): \[[21^*_7]_n=\{2,15,106,743,5202,\ldots\}\]

First few terms (base 7): \[\{\text{2},\text{21},\text{211},\text{2111},\text{21111},\ldots\}\]

General Formula:\[[21^*_7]_n={13\cdot7^{n}-1\over6}\]

Equivalent Patterns: \[[42^*_7]_n=2\cdot[21^*_7]_n\] \[[63^*_7]_n=3\cdot[21^*_7]_n\]

Table

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