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A247263 Positive numbers not divisible by 10 whose squares remain squares when prefixed with 1000. 5
375, 2371875, 6816208478590683385931482169914619837072677910327911376953125, 140221743281593822163509288486586064542459780568606220185756683349609375, 818488127823449514709977488133381451695186814276894438080489635467529296875 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Chai Wah Wu, Table of n, a(n) for n = 1..53

EXAMPLE

375^2 = 140625 and 1000140625 is square.

PROG

(PARI)

for(n=1, 10^20, if(n^2%100&&issquare(10^(#Str(n^2)+3)+n^2), print1(n^2, ", "))) \\ Derek Orr, Sep 13 2014

CROSSREFS

Cf. A242268, A247261, A247262, A247264.

Sequence in context: A249550 A045200 A252071 * A251652 A251645 A259769

Adjacent sequences:  A247260 A247261 A247262 * A247264 A247265 A247266

KEYWORD

nonn,base

AUTHOR

Chai Wah Wu, Sep 11 2014

STATUS

approved

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Last modified July 7 16:01 EDT 2020. Contains 335496 sequences. (Running on oeis4.)