A044138 Numbers n such that string 0,0 occurs in the base 7 representation of n but not of n-1.

49, 98, 147, 196, 245, 294, 343, 392, 441, 490, 539, 588, 637, 686, 735, 784, 833, 882, 931, 980, 1029, 1078, 1127, 1176, 1225, 1274, 1323, 1372, 1421, 1470, 1519, 1568, 1617, 1666, 1715, 1764, 1813, 1862, 1911, 1960, 2009, 2058, 2107, 2156, 2205, 2254, 2303

Offset

1,1

Comments

Every element is a multiple of 49. The smallest positive multiple of 49 not in the sequence is 2450. - David W. Wilson, Aug 03 2005

Links

Table of n, a(n) for n=1..47.

Tanya Khovanova, Non Recursions

Mathematica

f[n_] := Length[StringPosition[ToString[FromDigits[IntegerDigits[n, 7]]], "00", 1]]; Select[Table[n, {n, 10000}], f[#] > 0 && f[# - 1] == 0 &] (* Vladimir Joseph Stephan Orlovsky, Jul 23 2011 *)
Select[Range[2500], MemberQ[Partition[IntegerDigits[#, 7], 2, 1], {0, 0}] && !MemberQ[ Partition[IntegerDigits[#-1, 7], 2, 1], {0, 0}]&] (* Harvey P. Dale, Jan 21 2014 *)
SequencePosition[Table[If[SequenceCount[IntegerDigits[n, 7], {0, 0}]>0, 1, 0], {n, 2500}], {0, 1}][[;; , 2]] (* Harvey P. Dale, May 28 2024 *)

Crossrefs

Sequence in context: A131601 A309541 A174386 * A043394 A044519 A031484

Adjacent sequences: A044135 A044136 A044137 * A044139 A044140 A044141

Keyword

nonn,base

Author

Clark Kimberling

Status

approved