A260529 - OEIS

A260529

Concatenate the positions of digits 9, 8,..., 0 in the decimal representation of n, using 1 for the rightmost digit etc., skip it if a digit does not occur.

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, 21, 21, 21, 21, 21, 12, 12, 12, 12, 12, 21, 21, 21, 21, 21, 21, 12

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OFFSET

0,11

COMMENTS

Sequence A260275 lists fixed points of this function.

LINKS

Table of n, a(n) for n=0..66.

EXAMPLE

Consider n=1103, digits 4-9 do not occur, the digit '3' is at the 1st position (looking from the right), digit '2' does not occur, digit '1' is in 3rd and 4th place, digit '0' at 2nd position. Thus a(1103) = 1342.

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)); if(1<#p=concat(Vecrev(select(t->#t, p))), p[1]=Str(p[1]); eval(concat(p)), p)}

CROSSREFS

Cf. A260526 - A260528 and A260519 - A260522 for variants; A045918 for the classical "look and say" sequence.

Sequence in context: A301497 A258083 A260527 * A166033 A228092 A071262

Adjacent sequences: A260526 A260527 A260528 * A260530 A260531 A260532

KEYWORD

nonn,base

AUTHOR

M. F. Hasler, Jul 28 2015

STATUS

approved