OFFSET
1,2
LINKS
David A. Corneth, Table of n, a(n) for n = 1..10000
EXAMPLE
117 is in the sequence because it has a run length of 2 and a run length of 1. 101 is not in the sequence because it has three run lengths of 1. - R. J. Mathar, Jan 18 2018
MAPLE
rlset := proc(L::list)
local lset, rl, i ;
lset := [] ;
rl := 1 ;
for i from 2 to nops(L) do
if op(i, L) = op(i-1, L) then
rl := rl+1 ;
else
lset := [op(lset), rl] ;
rl := 1;
end if;
end do:
lset := [op(lset), rl] ;
end proc:
isA044821 := proc(n)
local dgs, rl;
dgs := convert(n, base, 10) ;
rl := rlset(dgs) ;
if nops(rl) = nops( convert(rl, set)) then
true;
else
false;
end if;
end proc:
for n from 1 to 400 do
if isA044821(n) then
printf("%d, ", n) ;
end if;
end do: # R. J. Mathar, Jan 18 2018
PROG
(Python)
from itertools import groupby
def ok(n):
runlengths = [len(list(g)) for k, g in groupby(str(n))]
return len(runlengths) == len(set(runlengths))
print([i for i in range(1, 256) if ok(i)]) # Michael S. Branicky, Jan 04 2021
(PARI) is(n) = { my(runs = List(), lr = 0, d = digits(n)); for(i = 1, #d - 1, if(d[i] != d[i + 1], listput(runs, i - lr); lr = i; ) ); listput(runs, #d - lr); #Set(runs) == #runs } \\ David A. Corneth, Jan 04 2021
CROSSREFS
KEYWORD
nonn,base
AUTHOR
STATUS
approved