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A173668 Smallest n-digit square such that no number made by chopping off a group of one or more digits from the left is a square. 0
16, 196, 1156, 12996, 104976, 1069156, 10010896, 102292996, 1000077376, 10064904976, 100003942756, 1002069069156, 10000040096656, 100063290010896, 1000000467910656, 10002022902292996, 100000005048995076, 1000063249000077376, 10000000024233296896 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

COMMENTS

Ending in 6 is a must for a number to be part of this sequence

LINKS

Table of n, a(n) for n=2..20.

EXAMPLE

a(5) cannot be 104^2 = 10816 because 16 (the last 2 digits) makes a square. 114^2 = 12996 qualifies.

MATHEMATICA

bad[n_] := Block[{q = n^2, p = 10}, While[p < q, If[IntegerQ@Sqrt@Mod[q, p], Break[], p *= 10]]; p < q]; a[n_] := Block[{k = Ceiling[10^((n - 1)/2)]}, While[bad@k, k++]; k^2]; a /@ Range[2, 20] (* Giovanni Resta, Mar 11 2013 *)

CROSSREFS

Sequence in context: A077363 A068989 A017318 * A126981 A086940 A016173

Adjacent sequences:  A173665 A173666 A173667 * A173669 A173670 A173671

KEYWORD

nonn,base

AUTHOR

J. Lowell, Nov 24 2010

EXTENSIONS

a(12)-a(20) from Giovanni Resta, Mar 11 2013

STATUS

approved

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Last modified June 22 16:35 EDT 2021. Contains 345388 sequences. (Running on oeis4.)