A062118 - OEIS

A062118

Numbers k such that k^2 has k as its middle digits.

1, 50, 60, 250, 3792, 7600, 376000, 495475, 625000, 971582, 66952741, 93760000, 177656344, 3199268655, 9062500000, 10937600000, 788138178328, 860628177919, 890625000000, 2291665833333, 2780225311054, 2890625000000, 71093760000000, 128906250000000

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OFFSET

1,2

COMMENTS

Some of the terms are automorphic numbers (A003226) multiplied by an appropriate power of 10. a(25) > 10^15. - Giovanni Resta, Jul 29 2013

REFERENCES

Computed by Robert Israel.

LINKS

Table of n, a(n) for n=1..24.

EXAMPLE

a(5)=3792 because 3792^2 = 14379264 has 3792 as its middle digits.

MATHEMATICA

Do[ If[ StringPosition[ ToString[n^2], ToString[n]] [[1, 1]] == (Ceiling[ Log[10, n^2] ] - Ceiling[ Log[10, n] ])/2 + 1, Print[n] ], {n, 1, 10^9} ]

CROSSREFS

k^2 is given in A062120.

Sequence in context: A046832 A046834 A046836 * A167329 A179796 A215468

Adjacent sequences: A062115 A062116 A062117 * A062119 A062120 A062121

KEYWORD

nonn,base,nice

AUTHOR

Brian Wallace (wallacebrianedward(AT)yahoo.co.uk), Jun 28 2001

EXTENSIONS

Corrected and extended by Robert G. Wilson v, Aug 08 2001

a(15)-a(24) from Giovanni Resta, Jul 29 2013

STATUS

approved