A297250 Numbers whose base-3 digits having equal up-variation and down-variation; see Comments.

1, 2, 4, 8, 10, 13, 16, 20, 23, 26, 28, 31, 34, 37, 40, 43, 46, 49, 52, 56, 59, 62, 65, 68, 71, 74, 77, 80, 82, 85, 88, 91, 94, 97, 100, 103, 106, 109, 112, 115, 118, 121, 124, 127, 130, 133, 136, 139, 142, 145, 148, 151, 154, 157, 160, 164, 167, 170, 173

Offset

1,2

Comments

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.

Links

Clark Kimberling, Table of n, a(n) for n = 1..10000

Example

173 in base-3:  2,0,1,0,2, having DV = 3, UV = 3, so that 173 is in the sequence.

Mathematica

g[n_, b_] := Map[Total, GatherBy[Differences[IntegerDigits[n, b]], Sign]];
x[n_, b_] := Select[g[n, b], # < 0 &]; y[n_, b_] := Select[g[n, b], # > 0 &];
b = 3; z = 2000; p = Table[x[n, b], {n, 1, z}]; q = Table[y[n, b], {n, 1, z}];
w = Sign[Flatten[p /. {} -> {0}] + Flatten[q /. {} -> {0}]];
Take[Flatten[Position[w, -1]], 120]   (* A297249 *)
Take[Flatten[Position[w, 0]], 120]    (* A297250 *)
Take[Flatten[Position[w, 1]], 120]    (* A297251 *)

Crossrefs

Cf. A297249, A297251, A297330.

Sequence in context: A219617 A100278 A075333 * A014190 A141400 A190744

Adjacent sequences: A297247 A297248 A297249 * A297251 A297252 A297253

Keyword

nonn,base,easy

Author

Clark Kimberling, Jan 15 2018

Status

approved