A297249 Numbers whose base-3 digits have greater down-variation than up-variation; see Comments.

3, 6, 7, 9, 12, 15, 18, 19, 21, 22, 24, 25, 27, 30, 33, 36, 39, 42, 45, 48, 51, 54, 55, 57, 58, 60, 61, 63, 64, 66, 67, 69, 70, 72, 73, 75, 76, 78, 79, 81, 84, 87, 90, 93, 96, 99, 102, 105, 108, 111, 114, 117, 120, 123, 126, 129, 132, 135, 138, 141, 144, 147

Offset

1,1

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

147 in base-3:  1,3,1,1,0, having DV = 3, UV = 2, so that 147 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. A297250, A297251, A297330.

Sequence in context: A026227 A026232 A286802 * A061641 A325443 A085359

Adjacent sequences: A297246 A297247 A297248 * A297250 A297251 A297252

Keyword

nonn,base,easy

Author

Clark Kimberling, Jan 15 2018

Status

approved