A260521 Concatenate the positions of digits 9, 8,..., 0 in the decimal representation of n, using 1 for the rightmost digit etc., and 0 when the digit does not occur.

1, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000, 1000000000, 21, 120, 120, 1020, 10020, 100020, 1000020, 10000020, 100000020, 1000000020, 201, 210, 1200, 1200, 10200, 100200, 1000200, 10000200, 100000200, 1000000200

Offset

0,2

Links

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

Example

Consider n=1103, digits '9' through '4' do not occur, digit '3' at 1st position (looking from the right), digit '2' does not occur, digit '1' in 3rd and 4th place, and digit '0' is at 2nd position. Thus a(1103) = 00000010342 = 10342.

Prog

(PARI) A260521=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(Vecrev(p)); p[1]=Str(p[1]); eval(concat(p))}

Crossrefs

Cf. A045918 (the classical "look and say" sequence).

Cf. A260519 - A260522 for variants (counting from the right or starting with digit 0).

Sequence in context: A086067 A348783 A260522 * A136873 A135655 A178500

Adjacent sequences: A260518 A260519 A260520 * A260522 A260523 A260524

Keyword

nonn,base

Author

M. F. Hasler, Jul 28 2015

Status

approved