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A225608
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The largest n-digit number whose first k digits are divisible by k.
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1
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9, 98, 987, 9876, 98765, 987654, 9876545, 98765456, 987654564, 9876545640, 98765456405, 987606963096, 9876069630960, 98760696309604, 987606963096045, 9876062430364208, 98485872309636009, 984450645096105672, 9812523240364656789, 96685896604836004260
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OFFSET
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1,1
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COMMENTS
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There are 25 terms in the sequence; the 25-digit number 3608528850368400786036725 is the largest number to satisfy the requirements.
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LINKS
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EXAMPLE
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There are nine one-digit numbers divisible by 1; the largest is 9 so a(1)=9.
For two-digit numbers, the second digit must be even (0,2,4,6,8) to make it divisible by 2, which gives 98 as the largest to satisfy the requirement, so a(2)=98.
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MATHEMATICA
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a=Table[j, {j, 9}]; r=2; t={}; While[!a == {}, n=Length[a]; nmax=Last[a]; k=1; b={}; While[!k>n, z0=a[[k]]; Do[z=10*z0+j; If[Mod[z, r]==0, b=Append[b, z]], {j, 0, 9}]; k++]; AppendTo[t, nmax]; a=b; r++]; t
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CROSSREFS
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KEYWORD
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nonn,base,fini
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AUTHOR
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STATUS
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approved
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