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A260528 Concatenate the positions of digits 9, 8,..., 0 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, 12, 12, 21, 21, 21, 21, 21, 21, 21, 21, 12, 12, 12, 21, 21, 21, 21, 21, 21, 21, 12, 12, 12, 12, 21, 21, 21, 21, 21, 21, 12, 12, 12, 12, 12, 21, 21, 21, 21, 21, 12, 12, 12, 12, 12, 12, 21, 21, 21, 21, 12, 12, 12, 12, 12 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,11

LINKS

Table of n, a(n) for n=0..64.

EXAMPLE

Consider n=1103: the digit '3' is at the 4th position (looking from the left), digit '1' is in 1st and 2nd place, digit '0' is at 3rd position, digits 2 and 4-9 do not occur. Thus a(1103) = 4123.

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(Vecrev(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: A056627 A061074 A064161 * A260526 A040133 A092538

Adjacent sequences:  A260525 A260526 A260527 * A260529 A260530 A260531

KEYWORD

nonn,base

AUTHOR

M. F. Hasler, Jul 28 2015

STATUS

approved

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Last modified July 21 06:55 EDT 2019. Contains 325192 sequences. (Running on oeis4.)