login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A297262 Numbers whose base-7 digits have equal up-variation and down-variation; see Comments. 4

%I

%S 1,2,3,4,5,6,8,16,24,32,40,48,50,57,64,71,78,85,92,100,107,114,121,

%T 128,135,142,150,157,164,171,178,185,192,200,207,214,221,228,235,242,

%U 250,257,264,271,278,285,292,300,307,314,321,328,335,342,344,351,358

%N Numbers whose base-7 digits have equal up-variation and down-variation; see Comments.

%C Suppose that n has base-b digits b(m), b(m-1), ..., b(0). The base-b down-variation of n is the sum DV(n,b) of all d(i)-d(i-1) for which d(i) > d(i-1); the base-b up-variation of n is the sum UV(n,b) of all d(k-1)-d(k) for which d(k) < d(k-1). The total base-b variation of n is the sum TV(n,b) = DV(n,b) + UV(n,b). See the guide at A297330.

%H Clark Kimberling, <a href="/A297262/b297262.txt">Table of n, a(n) for n = 1..10000</a>

%e 358 in base-7: 1,0,2,1, having DV = 2, UV = 2, so that 358 is in the sequence.

%t g[n_, b_] := Map[Total, GatherBy[Differences[IntegerDigits[n, b]], Sign]];

%t x[n_, b_] := Select[g[n, b], # < 0 &]; y[n_, b_] := Select[g[n, b], # > 0 &];

%t b = 7; z = 2000; p = Table[x[n, b], {n, 1, z}]; q = Table[y[n, b], {n, 1, z}];

%t w = Sign[Flatten[p /. {} -> {0}] + Flatten[q /. {} -> {0}]];

%t Take[Flatten[Position[w, -1]], 120] (* A297261 *)

%t Take[Flatten[Position[w, 0]], 120] (* A297262 *)

%t Take[Flatten[Position[w, 1]], 120] (* A297263 *)

%Y Cf. A297330, A297261, A297263.

%K nonn,base,easy

%O 1,2

%A _Clark Kimberling_, Jan 15 2018

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified August 10 11:57 EDT 2022. Contains 356039 sequences. (Running on oeis4.)