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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Most first differences are alternatively 18 and 32.

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

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

Adjacent sequences:  A159772 A159773 A159774 * A159776 A159777 A159778

KEYWORD

base,nonn

AUTHOR

Zak Seidov, Apr 21 2009

STATUS

approved

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Last modified August 7 19:57 EDT 2020. Contains 336279 sequences. (Running on oeis4.)