A297252 Numbers whose base-4 digits have greater down-variation than up-variation; see Comments.

4, 8, 9, 12, 13, 14, 16, 20, 24, 28, 32, 33, 36, 37, 40, 41, 44, 45, 48, 49, 50, 52, 53, 54, 56, 57, 58, 60, 61, 62, 64, 68, 72, 76, 80, 84, 88, 92, 96, 100, 104, 108, 112, 116, 120, 124, 128, 129, 132, 133, 136, 137, 140, 141, 144, 145, 148, 149, 152, 153

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

153 in base-4:  2,1,2,1, having DV = 2, UV = 1, so that 153 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 = 4; 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]   (* A297252 *)
Take[Flatten[Position[w, 0]], 120]    (* A297253 *)
Take[Flatten[Position[w, 1]], 120]    (* A297254 *)

Crossrefs

Cf. A297330, A297253, A297254.

Sequence in context: A229004 A306976 A266142 * A296696 A297129 A078137

Adjacent sequences: A297249 A297250 A297251 * A297253 A297254 A297255

Keyword

nonn,base,easy

Author

Clark Kimberling, Jan 15 2018

Status

approved