A260519 Concatenate the positions of digits 0, 1,..., 9 in the decimal representation of n, using 1 for the rightmost digit etc., and 0 when the digit does not occur.

1000000000, 100000000, 10000000, 1000000, 100000, 10000, 1000, 100, 10, 1, 1200000000, 1200000000, 210000000, 201000000, 200100000, 200010000, 200001000, 200000100, 200000010, 200000001, 1020000000, 120000000, 120000000, 21000000, 20100000, 20010000, 20001000, 20000100, 20000010, 20000001

Offset

0,1

Links

Table of n, a(n) for n=0..29.

Example

Consider n=1103, the digit '0' is at 2nd position (looking from the right), digit '1' in 3rd and 4th place, digit '2' does not occur, digit '3' at 1st position, digits 4-9 do not occur. Thus a(1103) = 23401000000.

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)); p=concat(p); p[1]=Str(p[1]); eval(concat(p))}

Crossrefs

Cf. A260520 - A260522 for variants; A045918 for the classical "look and say" sequence.

Sequence in context: A307478 A375380 A100909 * A260520 A033423 A030455

Adjacent sequences: A260516 A260517 A260518 * A260520 A260521 A260522

Keyword

nonn,base

Author

M. F. Hasler, Jul 28 2015

Status

approved