A228008 The smallest n-digit number whose first k digits are divisible by k^2 for k = 1..n.

1, 12, 126, 1264, 24325, 243252, 6480005

Offset

1,2

Comments

There are 7 terms in the sequence and the 7-digit number 6480005 is the last 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 smallest is 1 so a(1)=1.
For two-digit numbers, the second digit must make it divisible by 2^2, which gives 12 as the smallest to satisfy the requirement, so a(2)=12.

Mathematica

a = Table[j, {j, 9}]; r = 2; t = {}; While[! a == {}, n = Length[a]; nmin = First[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, nmin]; a = b; r++]; t

Crossrefs

Cf. A079042.

Sequence in context: A348463 A159736 A004991 * A101602 A264896 A062199

Adjacent sequences: A228005 A228006 A228007 * A228009 A228010 A228011

Keyword

nonn,base,fini,full

Author

Shyam Sunder Gupta, Aug 08 2013

Status

approved