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, 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

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: A061074 A372219 A064161 * A260526 A040133 A092538

Adjacent sequences: A260525 A260526 A260527 * A260529 A260530 A260531

Keyword

nonn,base

Author

M. F. Hasler, Jul 28 2015

Status

approved