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A043940 Numbers k such that 1 and 3 occur juxtaposed in the base-8 representation of k but not of k+1. 2
11, 25, 75, 95, 139, 153, 207, 217, 267, 281, 331, 345, 395, 409, 459, 473, 523, 537, 587, 607, 651, 665, 767, 779, 793, 843, 857, 907, 921, 971, 985, 1035, 1049, 1099, 1119, 1163, 1177, 1231, 1241, 1291, 1305, 1355, 1369, 1419, 1433, 1483, 1497, 1547, 1561 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
MATHEMATICA
SequencePosition[Table[If[SequenceCount[IntegerDigits[n, 8], {1, 3}]>0 || SequenceCount[IntegerDigits[n, 8], {3, 1}]>0, 1, 0], {n, 1400}], {1, 0}][[All, 1]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Sep 07 2020 *)
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
Sequence in context: A105270 A039337 A043160 * A220434 A191720 A066956
KEYWORD
nonn,base
AUTHOR
STATUS
approved

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Last modified February 23 17:43 EST 2024. Contains 370283 sequences. (Running on oeis4.)