A260522 Concatenate the positions of digits 9, 8,..., 0 in the decimal representation of n, using 1 for the leftmost digit etc., and 0 when the digit does not occur.

1, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000, 1000000000, 12, 120, 210, 2010, 20010, 200010, 2000010, 20000010, 200000010, 2000000010, 102, 120, 1200, 2100, 20100, 200100, 2000100, 20000100, 200000100, 2000000100

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 4th position, digit '2' does not occur, digit '1' in 1st and 2nd place, and digit '0' is at 3rd position. Thus a(1103) = 00000040123 = 40123.

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

Crossrefs

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

Cf. A260519 - A260521 for variants (counting from the right or starting with digit 0).

Sequence in context: A125858 A086067 A348783 * A260521 A136873 A135655

Adjacent sequences: A260519 A260520 A260521 * A260523 A260524 A260525

Keyword

nonn,base

Author

M. F. Hasler, Jul 28 2015

Status

approved