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A159815 Numbers n with property that n^2 starts and ends with 49. 1

%I #6 Apr 22 2016 12:36:37

%S 7,707,7007,7043,7057,22143,22157,22193,22207,22243,22257,22293,22307,

%T 22343,22357,70007,70043,70057,70093,70107,70143,70157,70193,70207,

%U 70243,70257,70293,70307,70343,70357,70393,70407,70443,70457,70493

%N Numbers n with property that n^2 starts and ends with 49.

%C Most first differences are alternatively 14 and 36.

%H Harvey P. Dale, <a href="/A159815/b159815.txt">Table of n, a(n) for n = 1..1000</a>

%e {7,707,7007,7043,7057,22143,22157}^2={49,499849,49098049,49603849,49801249,490312449,490932649}.

%t s7={};Do[If[Take[IntegerDigits[n^2],2]=={4,9}&&PowerMod[n,2,100]==49,AppendTo[s7,n]],{n,7,300000}];s7

%t se49Q[n_]:=Module[{id=IntegerDigits[n^2]},Take[id,2]==Take[id,-2] == {4,9}]; Select[Range[5,71000],se49Q] (* _Harvey P. Dale_, Apr 22 2016 *)

%Y A159775 Numbers n with property that n^2 starts and ends with 81. A159754 Numbers n with property that n^2 ends with 81. A159254 Numbers n with property that n^2 ends with 49. A111445 n-th row contains first n numbers whose squares end in n^2.

%K base,nonn

%O 1,1

%A _Zak Seidov_, Apr 22 2009

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Last modified March 28 14:38 EDT 2024. Contains 371254 sequences. (Running on oeis4.)