A114433 Last digit (the checksum) of 10-digit ISBN numbers, 10 is represented as "X".

9, 7, 5, 3, 1, 10, 8, 6, 4, 8, 6, 4, 2, 0, 9, 7, 5, 3, 1, 5, 3, 1, 10, 8, 6, 4, 2, 0, 9, 2, 0, 9, 7, 5, 3, 1, 10, 8, 6, 10, 8, 6, 4, 2, 0, 9, 7, 5, 3, 7, 5, 3, 1, 10, 8, 6, 4, 2, 0, 4, 2, 0, 9, 7, 5, 3, 1, 10, 8, 1, 10, 8, 6, 4, 2, 0, 9, 7, 5, 9, 7, 5, 3, 1, 10, 8, 6, 4, 2, 6, 4, 2, 0, 9, 7, 5, 3, 1, 10

Offset

1,1

Links

Table of n, a(n) for n=1..99.

Formula

The first nine digits of ten-digit ISBN numbers are assigned according to the language, publisher and book. The final digit is a checksum: 1 x the first digit, 2 x the second digit, ... 9 x the ninth digit, reduced modulo 11 and 10 is printed as "X".

Prog

(Python)
def a(n): return sum((i+1)*int(s) for i, s in enumerate(str(n).zfill(9)))%11
print([a(n) for n in range(1, 100)]) # Michael S. Branicky, Sep 07 2021

Crossrefs

Sequence in context: A237841 A109846 A096230 * A222129 A188141 A244667

Adjacent sequences: A114430 A114431 A114432 * A114434 A114435 A114436

Keyword

easy,nonn,base

Author

Jud McCranie, Feb 13 2006

Status

approved