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 A260520 Concatenate the positions of digits 0, 1, ..., 9 in the decimal representation of n, using 1 for the leftmost digit etc., and 0 when the digit does not occur. 1
 1000000000, 100000000, 10000000, 1000000, 100000, 10000, 1000, 100, 10, 1, 2100000000, 1200000000, 120000000, 102000000, 100200000, 100020000, 100002000, 100000200, 100000020, 100000002, 2010000000, 210000000, 120000000, 12000000, 10200000, 10020000, 10002000, 10000200, 10000020, 10000002 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 LINKS EXAMPLE Consider n=1103: the digit '0' is at the 3rd position, digit '1' in the 1st and 2nd places, digit '2' does not occur, digit '3' at the 4th position, digits 4-9 do not occur. Thus a(1103) = 31204000000. 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)); p=concat(p); p[1]=Str(p[1]); eval(concat(p))} CROSSREFS Cf. A260519, A260521 and A260522 for variants. Cf. A045918 for the classical "look and say" sequence. Sequence in context: A307478 A100909 A260519 * A033423 A030455 A250600 Adjacent sequences:  A260517 A260518 A260519 * A260521 A260522 A260523 KEYWORD nonn,base AUTHOR M. F. Hasler, Jul 28 2015 STATUS approved

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Last modified November 30 08:19 EST 2021. Contains 349419 sequences. (Running on oeis4.)