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A264600 Let S_n denote the list of decimal numbers 0 to n, written backwards (allowing leading zeros) and arranged in lexicographic order; a(n) = position where backwards-n appears, starting indexing at 0. 3
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 2, 5, 8, 11, 14, 17, 20, 23, 26, 29, 3, 7, 11, 15, 19, 23, 27, 31, 35, 39, 4, 9, 14, 19, 24, 29, 34, 39, 44, 49, 5, 11, 17, 23, 29, 35, 41, 47, 53, 59, 6, 13, 20, 27, 34, 41, 48, 55, 62, 69, 7, 15, 23, 31, 39, 47, 55, 63, 71, 79, 8, 17, 26, 35, 44, 53, 62, 71, 80, 89, 9, 19, 29, 39, 49, 59, 69, 79, 89, 99, 1, 12 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Chai Wah Wu and Alois P. Heinz, Table of n, a(n) for n = 0..20000 (first 10000 terms from Chai Wah Wu)

FORMULA

a(0) = 0, a(10n+m) = a(n) + m*(n+1) for m in {0,...,9}. - Alois P. Heinz, Nov 20 2015

EXAMPLE

S_0 = [0], so a(0)=0,

...

S_9 = [0,1,2,3,4,5,6,7,8,9], so a(9) = 9,

S_10 = [0,01,1,2,3,4,5,6,7,8,9], so a(10) = 1,

S_11 = [0,01,1,11,2,3,4,5,6,7,8,9], so a(10) = 1,

...

S_20 = [0,01,02,1,11,2,21,3,31,4,41,5,51,6,61,7,71,8,81,9,91], so a(20) = 2, and so on

MAPLE

a:= proc(n) option remember; `if`(n=0, 0,

      irem(n, 10, 'r')*(r+1)+a(r))

    end:

seq(a(n), n=0..101);  # Alois P. Heinz, Nov 20 2015

PROG

(Python)

def A264600(n):

    return sorted(str(i)[::-1] for i in range(n+1)).index(str(n)[::-1]) # Chai Wah Wu, Nov 20 2015

CROSSREFS

Decimal analog of A264596.

Has same beginning as A061486 but is ultimately different: see A264668.

Sequence in context: A259043 A156207 A061486 * A138470 A325454 A112875

Adjacent sequences:  A264597 A264598 A264599 * A264601 A264602 A264603

KEYWORD

nonn,base

AUTHOR

N. J. A. Sloane, Nov 20 2015

EXTENSIONS

More terms from Alois P. Heinz, Nov 20 2015

STATUS

approved

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Last modified April 7 04:20 EDT 2020. Contains 333292 sequences. (Running on oeis4.)