[seqfan] Re: Middle digit in square numbers

Lars Blomberg larsl.blomberg at comhem.se
Mon Dec 12 11:18:39 CET 2016


OK.

So 10 A-numbers will be needed.
It would facilitate greatly if a sequence like Axxxxx0 .. Axxxxx9 could be allocated for this.
Is that possible, if so, how?
Regards,
Lars Blomberg

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Ämne: [seqfan] Re: Middle digit in square numbers

Not at all too simple.  Please do contribute them.

Cheers,
Robert

On Dec 11 2016, Lars Blomberg wrote:

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


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