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A297139 Numbers whose base-7 digits d(m), d(m-1),..., d(0) have m=0 or else d(i) = d(i+1) for some i in {0,1,...,m-1}. 4
1, 2, 3, 4, 5, 6, 8, 16, 24, 32, 40, 48, 49, 56, 57, 58, 59, 60, 61, 62, 65, 73, 81, 89, 97, 98, 106, 112, 113, 114, 115, 116, 117, 118, 122, 130, 138, 146, 147, 155, 163, 168, 169, 170, 171, 172, 173, 174, 179, 187, 195, 196, 204, 212, 220, 224, 225, 226 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

These numbers comprise the complement of the set of numbers in the union of A297137 and A297138.

Differs from A044818 first for 344 = 1001_7. 1001_7 has two runs of length 1 and is not in A044818, but it has a sequence of two consecutive zeros and is in this sequence. - R. J. Mathar, Jan 18 2018

LINKS

Table of n, a(n) for n=1..58.

EXAMPLE

Base-7 digits of 4998: 2,0,4,0,0, so that 4998 is in the sequence.

MAPLE

read("transforms") :

isA297139 := proc(n)

        local dgs, ud;

        dgs := convert(n, base, 7) ;

        if nops(dgs) < 2 then

                return true;

        end if;

        if 0 in DIFF(dgs) then

                true;

        else

                false;

        end if;

end proc:

for n from 1 to 300 do

        if isA297139(n) then

                printf("%d, ", n) ;

        end if;

end do: # R. J. Mathar, Jan 18 2018

MATHEMATICA

a[n_, b_] := Sign[Differences[IntegerDigits[n, b]]]; z = 300;

b = 7; t = Table[a[n, b], {n, 1, 10*z}];

u = Select[Range[z], ! MemberQ[t[[#]], 0] && First[t[[#]]] == 1 &]   (* A297137 *)

v = Select[Range[z], ! MemberQ[t[[#]], 0] && First[t[[#]]] == -1 &]  (* A297138 *)

Complement[Range[z], Union[u, v]]  (* A297139 *)

CROSSREFS

Cf. A297137, A297138.

Sequence in context: A039089 A044956 A044818 * A048304 A043710 A296703

Adjacent sequences:  A297136 A297137 A297138 * A297140 A297141 A297142

KEYWORD

nonn,easy,base

AUTHOR

Clark Kimberling, Jan 15 2018

STATUS

approved

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Last modified December 10 20:48 EST 2019. Contains 329909 sequences. (Running on oeis4.)