A044115 - OEIS

A044115

Numbers k such that string 2,1 occurs in the base 6 representation of k but not of k-1.

13, 49, 78, 85, 121, 157, 193, 229, 265, 294, 301, 337, 373, 409, 445, 468, 510, 517, 553, 589, 625, 661, 697, 726, 733, 769, 805, 841, 877, 913, 942, 949, 985, 1021, 1057, 1093, 1129, 1158, 1165, 1201, 1237, 1273, 1309, 1345, 1374, 1381, 1417, 1453, 1489, 1525, 1561, 1590

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OFFSET

1,1

LINKS

Paolo Xausa, Table of n, a(n) for n = 1..10000

MATHEMATICA

A044115Q[k_] := StringContainsQ[IntegerString[k, 6], "21"] && StringFreeQ[IntegerString[k - 1, 6], "21"];

Select[Range[5000], A044115Q] (* Paolo Xausa, Sep 11 2025 *)

SequencePosition[Table[If[SequenceCount[IntegerDigits[n, 6], {2, 1}]>0, 1, 0], {n, 1600}], {0, 1}][[;; , 2]] (* Harvey P. Dale, Mar 23 2026 *)

CROSSREFS

Cf. A007092.

Sequence in context: A304131 A304219 A305480 * A044496 A158480 A009951