A228007 - OEIS

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A228007

The largest n-digit number whose first k digits are divisible by k^2 for k = 1..n.

9, 96, 963, 9632, 96325, 963252, 6480005

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OFFSET

1,1

COMMENTS

There are 7 terms in the sequence and the 7-digit number 6480005 is the largest number to satisfy the requirements.

LINKS

Table of n, a(n) for n=1..7.

EXAMPLE

There are nine one-digit numbers divisible by 1 and the largest is 9, so a(1)=9.

For two-digit numbers, the second digit must make it divisible by 2^2, which gives 96 as the largest to satisfy the requirement, so a(2)=96.

MATHEMATICA

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*r] == 0, b = Append[b, z]], {j, 0, 9}]; k++]; AppendTo[t, nmax]; a = b; r++]; t

CROSSREFS

Cf. A079042.

Sequence in context: A090448 A264219 A005545 * A073560 A069055 A228011

Adjacent sequences: A228004 A228005 A228006 * A228008 A228009 A228010

KEYWORD

nonn,base,fini,full

AUTHOR

Shyam Sunder Gupta, Aug 08 2013

STATUS

approved