The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation. Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”). Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A228007 The largest n-digit number whose first k digits are divisible by k^2 for k = 1..n. 0

%I

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

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

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

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

%e 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.

%t 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

%Y Cf. A079042.

%K nonn,base,fini,full

%O 1,1

%A _Shyam Sunder Gupta_, Aug 08 2013

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 4 19:40 EST 2021. Contains 349526 sequences. (Running on oeis4.)