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A260527
Concatenate the positions of digits 0, 1,..., 9 in the decimal representation of n, using 1 for the leftmost digit etc., skip digits which don't occur.
1
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 21, 12, 12, 12, 12, 12, 12, 12, 12, 12, 21, 21, 12, 12, 12, 12, 12, 12, 12, 12, 21, 21, 21, 12, 12, 12, 12, 12, 12, 12, 21, 21, 21, 21, 12, 12, 12, 12, 12, 12
OFFSET
0,11
EXAMPLE
Consider n=1103, the digit '0' is at 3rd position (looking from the left), digit '1' in 1st and 2nd place, digit '3' at 4th position, digits 2 and 4-9 do not occur. Thus a(1103) = 3124.
PROG
(PARI) a(n)={my(p=vector(10)); for(i=1, #n=if(n, digits(n), [0]), p[n[i]+1]=if(p[n[i]+1], concat(p[n[i]+1], i), i)); if(1<#p=concat(select(t->#t, p)), p[1]=Str(p[1]); eval(concat(p)), p)}
CROSSREFS
Cf. A260526 - A260529 and A260519 - A260522 for variants; A045918 for the classical "look and say" sequence.
Sequence in context: A300887 A301497 A258083 * A260529 A166033 A228092
KEYWORD
nonn,base
AUTHOR
M. F. Hasler, Jul 28 2015
STATUS
approved