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%I #13 Sep 07 2021 09:27:27
%S 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,
%T 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,
%U 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
%N Last digit (the checksum) of 10-digit ISBN numbers, 10 is represented as "X".
%F 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".
%o (Python)
%o def a(n): return sum((i+1)*int(s) for i, s in enumerate(str(n).zfill(9)))%11
%o print([a(n) for n in range(1, 100)]) # _Michael S. Branicky_, Sep 07 2021
%K easy,nonn,base
%O 1,1
%A _Jud McCranie_, Feb 13 2006
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