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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
OFFSET
2,1
COMMENTS
Ending in 6 is a must for a number to be part of this sequence
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 * A373108 A126981 A086940
KEYWORD
nonn,base
AUTHOR
J. Lowell, Nov 24 2010
EXTENSIONS
a(12)-a(20) from Giovanni Resta, Mar 11 2013
STATUS
approved