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A129326 a(n) = (2*n+1)*(n-1)!. +0
10
3, 5, 14, 54, 264, 1560, 10800, 85680, 766080, 7620480, 83462400, 997920000, 12933043200, 180583603200, 2702527027200, 43153254144000, 732297646080000, 13160434839552000, 249692574523392000, 4987449116762112000, 104614786351595520000, 2299092397726924800000 (list; graph; listen)
OFFSET

1,1

COMMENT

In 1998, with help of planar polynomial differential systems, I discovered three bidimensional polynomials. Two of them are odd, the third, based on a degenerate case, is normal. In one dimension, it can be written D(n,z) = sum[((n+2)^2-(i+1)^2)*z/(i+1)] i=0..n Its roots are all complex when n is even and all except one if n is odd. They are equally distributed (thanks to Jean-Charles Faugare [Faugere?] in 2000). We write the first 4 lines and the transformed terms after multiplication by n!

.........3........................................3

.........8..5/2..................................16.....5

........15..12/2...7/3...........................90....36...14

........24..21/2..16/3..9/4.....................576...252..128..54.....

The numerators of the columns of the first array are well known (A005563, A028347, A028360). But the first vertical sequence and the one of the highest diagonal of the second array are unknown.

Read Faugere. Vertical numerators are n(n+2p)=(n+p)^2-p^2 (positive n,p) from A005563,A028347,A028560,A028566,A098603,A098847,A098848,A098849,A098850,A120071,A132764,A132766,A132768,A132770,A132772. Rows numerators are triangle A120070, for frequencies of the spectral lines of hydrogen atom: Lyman,A005563, Balmer,A061037, Paschen,A061039, Brackett,A061041, Pfund,A061043, Humphreys,A061045, Hansen-Strong,A061047, A061049, .. (numerators).See,in A120070, First ten rows and more. [From Paul Curtz (bpcrtz(AT)free.fr), Mar 14 2009]

FORMULA

a(n)=A052649(n), n>1. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jun 14 2008

CROSSREFS

Sequence in context: A006395 A078718 A081393 this_sequence A167553 A118562 A115043

Adjacent sequences: A129323 A129324 A129325 this_sequence A129327 A129328 A129329

KEYWORD

nonn

AUTHOR

Paul Curtz (bpcrtz(AT)free.fr), May 26 2007

EXTENSIONS

More terms from N. J. A. Sloane (njas(AT)research.att.com), Nov 08 2007

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Last modified December 5 08:23 EST 2009. Contains 170348 sequences.


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