A260520 Concatenate the positions of digits 0, 1, ..., 9 in the decimal representation of n, using 1 for the leftmost digit etc., and 0 when the digit does not occur.

1000000000, 100000000, 10000000, 1000000, 100000, 10000, 1000, 100, 10, 1, 2100000000, 1200000000, 120000000, 102000000, 100200000, 100020000, 100002000, 100000200, 100000020, 100000002, 2010000000, 210000000, 120000000, 12000000, 10200000, 10020000, 10002000, 10000200, 10000020, 10000002

Offset: 0

Author

M. F. Hasler, Jul 28 2015

Keywords

• nonn
• base

Examples

			Consider n=1103: the digit '0' is at the 3rd position, digit '1' in the 1st and 2nd places, digit '2' does not occur, digit '3' at the 4th position, digits 4-9 do not occur. Thus a(1103) = 31204000000.
		

Crossrefs

Cf. A260519, A260521 and A260522 for variants.

Cf. A045918 for the classical "look and say" sequence.

Programs

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