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A260519
Concatenate the positions of digits 0, 1,..., 9 in the decimal representation of n, using 1 for the rightmost digit etc., and 0 when the digit does not occur.
9
1000000000, 100000000, 10000000, 1000000, 100000, 10000, 1000, 100, 10, 1, 1200000000, 1200000000, 210000000, 201000000, 200100000, 200010000, 200001000, 200000100, 200000010, 200000001, 1020000000, 120000000, 120000000, 21000000, 20100000, 20010000, 20001000, 20000100, 20000010, 20000001
OFFSET
0,1
EXAMPLE
Consider n=1103, the digit '0' is at 2nd position (looking from the right), digit '1' in 3rd and 4th place, digit '2' does not occur, digit '3' at 1st position, digits 4-9 do not occur. Thus a(1103) = 23401000000.
PROG
(PARI) a(n)={my(p=vector(10)); for(i=1, #n=if(n, Vecrev(digits(n)), [0]), p[n[i]+1]=if(p[n[i]+1], concat(p[n[i]+1], i), i)); p=concat(p); p[1]=Str(p[1]); eval(concat(p))}
CROSSREFS
Cf. A260520 - A260522 for variants; A045918 for the classical "look and say" sequence.
Sequence in context: A307478 A375380 A100909 * A260520 A033423 A030455
KEYWORD
nonn,base
AUTHOR
M. F. Hasler, Jul 28 2015
STATUS
approved