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

0,1

Links

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

Example

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.

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

Crossrefs

Cf. A260519, A260521 and A260522 for variants.

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

Sequence in context: A307478 A100909 A260519 * A033423 A030455 A250600

Adjacent sequences: A260517 A260518 A260519 * A260521 A260522 A260523

Keyword

nonn,base

Author

M. F. Hasler, Jul 28 2015

Status

approved