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A077486
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Largest n-digit square which leaves a square at every step if most significant digit and least significant digit are deleted until a one- or two-digit square is obtained. a(2n) = 0 if no such square exists. a(2n+1) = 9*10^2n only if no nontrivial candidate exists.
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2
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9, 81, 841, 8649, 64009, 0, 4004001, 0, 900000000, 0, 40000400001, 0, 9000000000000, 0, 400000040000001, 0, 90000000000000000, 0, 4000000004000000001, 0, 900000000000000000000, 0, 40000000000400000000001
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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FORMULA
| Beginning with term a(6) the following pattern applies: a(4k)=0; a(4k+1)=9*10^4k=(3*10^2k)^2; a(4k+2)=0; a(4k+3)=(2*10^(2k+1)+1)^2. - Ray Chandler (rayjchandler(AT)sbcglobal.net), Aug 03 2003
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EXAMPLE
| a(5) = 64009 as 64009, 400 and 0 all are squares. Though 90000 is a candidate, it is a trivial one.
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CROSSREFS
| Cf. A077485.
Sequence in context: A001514 A077364 A067478 * A187122 A113361 A180737
Adjacent sequences: A077483 A077484 A077485 * A077487 A077488 A077489
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KEYWORD
| base,nonn
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AUTHOR
| Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Nov 07 2002
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EXTENSIONS
| More terms from Ray Chandler (rayjchandler(AT)sbcglobal.net), Aug 03 2003
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