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, 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

Links

Table of n, a(n) for n=0..49.

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

Adjacent sequences: A260524 A260525 A260526 * A260528 A260529 A260530

Keyword

nonn,base

Author

M. F. Hasler, Jul 28 2015

Status

approved