

A297281


Numbers whose base13 digits have greater upvariation than downvariation; see Comments.


4



15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 43, 44, 45, 46, 47, 48, 49, 50, 51, 57, 58, 59, 60, 61, 62, 63, 64, 71, 72, 73, 74, 75, 76, 77, 85, 86, 87, 88, 89, 90, 99, 100, 101, 102, 103, 113, 114, 115, 116, 127, 128
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OFFSET

1,1


COMMENTS

Suppose that n has baseb digits b(m), b(m1), ..., b(0). The baseb downvariation of n is the sum DV(n,b) of all d(i)d(i1) for which d(i) > d(i1); the baseb upvariation of n is the sum UV(n,b) of all d(k1)d(k) for which d(k) < d(k1). The total baseb variation of n is the sum TV(n,b) = DV(n,b) + UV(n,b). See the guide at A297330.
Differs from A296751 for example at 171 = 102_13, which is in this sequence because UV(171,13) = 2 > DV(171,13)=1, but not in A296751 because the number of rises and falls are equal.  R. J. Mathar, Jan 23 2018


LINKS



EXAMPLE

128 in base13: 9,11, having DV = 0, UV = 2, so that 28 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 = 13; 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] (* A297279 *)
Take[Flatten[Position[w, 0]], 120] (* A297280 *)
Take[Flatten[Position[w, 1]], 120] (* A297281 *)


CROSSREFS



KEYWORD

nonn,base,easy


AUTHOR



STATUS

approved



