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-   MattcAnderson (https://www.mersenneforum.org/forumdisplay.php?f=146)

 MattcAnderson 2016-09-10 05:47

A034856/

Hi Math People,

I was exploring oeis.org. This is the Online Encyclopedia of integer sequences.

[URL="oeis.org/A034856/"]oeis.org/A034856/[/URL]

Many people have double checked this encyclopedia.

I read that for A034856, a(n) reduces to n*(n+3)/2 - 1.

When I work it through, I reach the expression n*(n-1)/2 -1.

Probably I am wrong and the encyclopedia is right.

I assume that binomial(n,k) = n!/(k!(n-k)!).
Can someone else check this expression?

Regards,
Matt

 GP2 2016-09-10 07:25

[QUOTE=MattcAnderson;442116][URL="oeis.org/A034856/"]oeis.org/A034856/[/URL]

I read that for A034856, a(n) reduces to n*(n+3)/2 - 1.

When I work it through, I reach the expression n*(n-1)/2 -1.
[/QUOTE]

[CODE]
binomial(n+1, 2) + (n − 1)

n*(n+1) 2*(n−1)
= ------- + -------
2 2

n*n + 1*n + 2*n − 2
= -------------------
2

n*(n+3) − 2
= -----------
2

n*(n+3)
= ------- − 1
2
[/CODE]

 MattcAnderson 2016-09-10 14:20

Thank you GP2. You are correct.

Regards,
Matt

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