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A159775
Numbers n with property that n^2 starts and ends with 81.
2
9, 2859, 9009, 9041, 28491, 28509, 28541, 28559, 28591, 28609, 90009, 90041, 90059, 90091, 90109, 90141, 90159, 90191, 90209, 90241, 90259, 90291, 90309, 90341, 90359, 90391, 90409, 90441, 90459, 90491, 90509, 90541, 284609, 284641, 284659
OFFSET
1,1
COMMENTS
Most first differences are alternatively 18 and 32.
LINKS
EXAMPLE
map(x-> x^2, {9,2859,9009,9041,28491}) = {81,8173881,81162081,81739681,811737081}.
MAPLE
f:= proc(d) local L, U, a, b;
L:= ceil(sqrt(81*10^(d-2)));
U:= floor(sqrt(82*10^(d-2)));
op(select(t -> t >= L and t <= U, [seq(seq(100*a+b, b=[9, 41, 59, 91]), a=ceil((L-91)/100)..floor((U-4)/100))]))
end proc:
seq(f(d), d=2..12); # Robert Israel, Jan 02 2018
MATHEMATICA
be9Q[n_]:=Module[{idn=IntegerDigits[n^2]}, Take[idn, 2]== Take[idn, -2] =={8, 1}]; nn=300000; Sort[Join[Select[Range[9, nn, 10], be9Q], Select[Range[ 11, nn, 10], be9Q]]] (* Harvey P. Dale, Apr 30 2011 *)
CROSSREFS
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.
Sequence in context: A033997 A068729 A321282 * A281538 A335010 A203744
KEYWORD
base,nonn
AUTHOR
Zak Seidov, Apr 21 2009
STATUS
approved