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A329447
Look left and tell the least frequent: after a(0) = 0, a(n) = 10c + d, where c > 0 is the number of times the least frequent digit d has appeared so far; smallest d in case of tie.
5
0, 10, 11, 20, 12, 22, 30, 13, 23, 33, 40, 14, 24, 34, 44, 50, 15, 25, 35, 45, 55, 60, 16, 26, 36, 46, 56, 66, 70, 17, 27, 37, 47, 57, 67, 77, 80, 18, 28, 38, 48, 58, 68, 78, 88, 90, 19, 29, 39, 49, 59, 69, 79, 89, 99, 100, 112, 113, 114, 115, 116, 117, 118, 119, 120, 123, 124, 125, 126, 127, 128, 129
OFFSET
0,2
COMMENTS
The terms "10c + d" are to be read "c digits d (have appeared so far)", as in the "look and see" sequences A045918 and similar.
An analog sequence may be computed for any other initial term a(0). Sequence A329448 lists the starting values that will appear a second time later in the respective sequence.
LINKS
M. F. Hasler, Table of n, a(n) for n = 0..10000 (independently computed by Jean-Marc Falcoz).
Eric Angelini, Look left and say, Nov 14 2019.
MAPLE
a[0]:= 0;
S[0]:= 1:
for i from 1 to 9 do S[i]:= 0 od:
for n from 1 to 100 do
a[n]:= min(select(`>=`, [seq(10*S[i]+i, i=0..9)], 10));
L:= convert(a[n], base, 10);
for d from 0 to 9 do S[d]:= S[d] + numboccur(d, L) od;
od:
seq(a[n], n=0..100); # Robert Israel, Nov 14 2019
PROG
(PARI) A329447_vec(N)={my(c=Vec(1, 10), t); vector(N, i, for(j=1, #i=vecsort(c, , 1), if(c[i[j]], i=i[j]; break)); for(j=1, #i=digits(t=c[i]*10+i-1), c[i[j]+1]++); t)} \\ Returns the vector a(1..N)
CROSSREFS
Cf. A045918 (describe n), A005150 (describe the preceding term), A139282 (count vowels so far), A139097 (count letters so far).
Sequence in context: A216996 A165265 A329818 * A352339 A197652 A261909
KEYWORD
nonn,base
AUTHOR
Eric Angelini and M. F. Hasler, Nov 14 2019
STATUS
approved