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A044159 Numbers n such that string 3,0 occurs in the base 7 representation of n but not of n-1. 0
21, 70, 119, 147, 168, 217, 266, 315, 364, 413, 462, 490, 511, 560, 609, 658, 707, 756, 805, 833, 854, 903, 952, 1001, 1029, 1099, 1148, 1176, 1197, 1246, 1295, 1344, 1393, 1442, 1491, 1519, 1540, 1589, 1638, 1687, 1736, 1785 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..42.

MATHEMATICA

Select[Range[2000], MemberQ[Partition[IntegerDigits[#, 7], 2, 1], {3, 0}] && !MemberQ[Partition[IntegerDigits[#-1, 7], 2, 1], {3, 0}]&] (* or *) Flatten[ Position[Partition[If[MemberQ[Partition[IntegerDigits[#, 7], 2, 1], {3, 0}], 1, 0]&/@Range[2000], 2, 1], {0, 1}]]+1 (* Harvey P. Dale, Aug 21 2013 *)

SequencePosition[Table[If[SequenceCount[IntegerDigits[n, 7], {3, 0}]>0, 1, 0], {n, 1800}], {0, 1}][[All, 2]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Sep 15 2019 *)

CROSSREFS

Sequence in context: A155492 A201066 A200931 * A044540 A195026 A296035

Adjacent sequences:  A044156 A044157 A044158 * A044160 A044161 A044162

KEYWORD

nonn,base

AUTHOR

Clark Kimberling

STATUS

approved

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Last modified July 29 04:15 EDT 2021. Contains 346340 sequences. (Running on oeis4.)