[seqfan] Re: In search of a formula for a number triangle

[Harvey P. Dale]

Al:

	Does this Mma program properly generate the terms of the sequence?
	
	Flatten[Table[{n,Range[10n,10n+n-2]},{n,20}]]

	Best,

	Harvey
 

-----Original Message-----
From: SeqFan [mailto:seqfan-bounces at list.seqfan.eu] On Behalf Of Alonso Del Arte
Sent: Monday, January 07, 2013 5:40 PM
To: Sequence Fanatics Discussion list
Subject: [seqfan] In search of a formula for a number triangle

The triangle of A077341

1

2 20

3 30 31

4 40 41 42

5 50 51 52 53

...

 19 190 191 ...

200 201 202 ...

 21 210 211 ...

...

and the related sequence A077342, initial rows of the triangle, has the question "Can anyone derive a formula for a(n)?" I can't, but I believe I may at least be able to figure out which a(n) = n. This is what I've come up with:

a(n) = n when n > 10 * floor(n/10) + floor(n/10) - 2.

But of course this only takes into account the nearest previous row that could possibly contain n. Is that enough or does this formula need to be amended to take into account even earlier rows?

Al

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