A180728 21^a(n) is smallest power of 21 beginning with n.
0, 1, 8, 2, 21, 15, 9, 6, 3, 28, 25, 22, 19, 16, 13, 10, 38, 7, 4, 32, 1, 29, 26, 85, 23, 82, 20, 79, 48, 17, 45, 14, 73, 42, 11, 39, 8, 67, 36, 5, 64, 33, 362, 2, 61, 30, 89, 58, 387, 27, 86, 55, 384, 24, 83, 52, 1191, 21, 80, 1219, 49, 288, 18, 77, 946, 46, 285, 15, 74, 1483, 43
Offset: 1
Links
- D. Mondot, Table of n, a(n) for n=1..32699
Programs
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Mathematica
Module[{nn=1500,t21},t21=Table[{n,IntegerDigits[21^n]},{n,0,nn}];Table[SelectFirst[ t21,IntegerDigits[k]==Take[#[[2]],IntegerLength[k]]&],{k,80}]][[;;,1]]//Quiet (* Harvey P. Dale, May 14 2023 *)