A043160 Numbers k such that 1 and 3 occur juxtaposed in the base-8 representation of k but not of k-1.

11, 25, 75, 88, 139, 153, 200, 217, 267, 281, 331, 345, 395, 409, 459, 473, 523, 537, 587, 600, 651, 665, 704, 779, 793, 843, 857, 907, 921, 971, 985, 1035, 1049, 1099, 1112, 1163, 1177, 1224, 1241, 1291, 1305, 1355, 1369, 1419, 1433, 1483, 1497, 1547, 1561

Offset

1,1

Links

Michael S. Branicky, Table of n, a(n) for n = 1..10000

Mathematica

SequencePosition[Table[If[SequenceCount[IntegerDigits[n, 8], {1, 3}]>0 || SequenceCount[ IntegerDigits[n, 8], {3, 1}]>0, 1, 0], {n, 1600}], {0, 1}][[All, 2]] (* Harvey P. Dale, Nov 11 2022 *)

Prog

(Python)
def has13or31(n): o = oct(n); return "13" in o or "31" in o
def ok(n): return has13or31(n) and not has13or31(n-1)
print([k for k in range(1600) if ok(k)]) # Michael S. Branicky, Nov 25 2021

Crossrefs

Cf. A007094, A043940.

Sequence in context: A262105 A105270 A039337 * A043940 A220434 A191720

Adjacent sequences: A043157 A043158 A043159 * A043161 A043162 A043163

Keyword

nonn,base

Author

Clark Kimberling

Status

approved