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

Author

M. F. Hasler, Jul 28 2015

Keywords

• nonn
• base

Examples

			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.
		

Crossrefs

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

Programs

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))}