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A077486 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. 2
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; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..23.

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, Aug 03 2003

EXAMPLE

a(5) = 64009 as 64009, 400 and 0 all are squares. Though 90000 is a candidate, it is a trivial one.

CROSSREFS

Cf. A077485.

Sequence in context: A137062 A001514 A077364 * A233021 A187122 A113361

Adjacent sequences:  A077483 A077484 A077485 * A077487 A077488 A077489

KEYWORD

base,nonn

AUTHOR

Amarnath Murthy, Nov 07 2002

EXTENSIONS

More terms from Ray Chandler, Aug 03 2003

STATUS

approved

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Last modified November 27 06:49 EST 2021. Contains 349365 sequences. (Running on oeis4.)