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A043698
Numbers whose base-9 representation has an even number of runs.
4
9, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 24, 25, 26, 27, 28, 29, 31, 32, 33, 34, 35, 36, 37, 38, 39, 41, 42, 43, 44, 45, 46, 47, 48, 49, 51, 52, 53, 54, 55, 56, 57, 58, 59, 61, 62, 63, 64, 65, 66, 67, 68, 69, 71, 72, 73, 74, 75, 76, 77, 78, 79, 81, 90, 92, 93, 94, 95, 96, 97, 98, 101, 111, 121, 131, 141
OFFSET
1,1
MAPLE
isA043698 := proc(n)
local dgs, runs, i ;
dgs := convert(n, base, 9) ;
runs :=1 ;
for i from 2 to nops(dgs) do
if op(i, dgs) <> op(i-1, dgs) then
runs := runs+1 ;
end if;
end do:
if type(runs, 'even') then
true;
else
false;
end if;
end proc:
A043698 := proc(n)
option remember;
local a;
if n = 1 then
9;
else
for a from procname(n-1)+1 do
if isA043698(a) then
return a ;
end if;
end do:
end if
end proc:
seq(A043698(n), n=1..120) ; # R. J. Mathar, Feb 20 2023
CROSSREFS
Sequence in context: A263772 A031954 A043631 * A043457 A202707 A031078
KEYWORD
nonn,base
STATUS
approved