# [seqfan] Re: Middle digit in square numbers

israel at math.ubc.ca israel at math.ubc.ca
Mon Dec 12 08:38:53 CET 2016

```Not at all too simple.  Please do contribute them.

Cheers,
Robert

On Dec 11 2016, Lars Blomberg wrote:

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>Hello,
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>Numbers k such that the middle digit of k^2 is d.
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>Obviously k^2 must have an odd number of digits.
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>Examples for d=4: 2^2 = 4, 12^2 = 144, 21^2 = 441, 29^2 = 841, 102 = 10404,
>...
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>Start of sequences for d =  0..9
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>0: 10, 20, 30, 100, 105, 138, 145, .
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>1: 1, 110, 119, 123, 127, 131, 142, .
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>2: 11, 15, 18, 23, 25, 27, 101, 106,.
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>3: 111, 124, 128, 139, 146, 156, 177, .
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>4: 2, 12, 21, 29, 102, 107, 116, 120,.
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>5: 16, 112, 150, 163, 166, 169, 172,.
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>6: 13, 19, 31, 103, 108, 117, 121, .
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>7: 24, 26, 113, 137, 144, 154, 181,.
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>8: 17, 22, 28, 104, 109, 122, 126, .
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>9: 3, 14, 114, 118, 130, 134, 148, .
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>It was a surprise to me that none of these sequences are in OEIS.
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>Maybe they are too simple to be included?
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>/Lars Blomberg
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>--
>Seqfan Mailing list - http://list.seqfan.eu/
>
>

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