cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A174381 Triangle for denominators of half extended Rydberg-Ritz spectrum of the hydrogenic spectra. a(n) is an antidiagonal writing of array in A171522 without first column.

Original entry on oeis.org

0, 0, 4, 0, 9, 36, 0, 16, 16, 144, 0, 25, 100, 225, 400, 0, 36, 9, 12, 144, 900, 0, 49, 196, 441, 784, 1225, 1764, 0, 64, 64, 576, 64, 1600, 576, 3136, 0, 81, 324, 81, 1296, 2025, 324, 3969, 5184, 0, 100, 25, 900, 400, 100, 225, 4900, 1600, 8100, 0, 121, 484, 1089
Offset: 0

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Author

Paul Curtz, Mar 17 2010

Keywords

Comments

Companion to A172157 (numerators). Hence -1/0; -1/0,-3/4; -1/0,-8/9,-5/36; -1/0,-15/16,-3/16,-7/144; -1/0,-24/25,-21/100,-16/225,-9/400; for 1) (-1/0, A005563/A000290(n+1))=A067998(n+1)/A000290 Lyman; 2) -1/0, -3/4, A061037/A061038 Balmer ; 3) -1/0, -8/9, -5/36, A061039/A061040)=A171709(n+3)/ Paschen; 4) (-1/0, -15/16, -3/16, -7/144, A061041/A061042 Brackett; .. .

Formula

a(n)= 0, (mix 0 or A000004 , n-th row of A120073)

A177842 Period 27: repeat 1, 81, 81, 3, 81, 81, 9, 81, 81, 3, 81, 81, 3, 81, 81, 9, 81, 81, 3, 81, 81, 1, 81, 81, 9, 81, 81.

Original entry on oeis.org

1, 81, 81, 3, 81, 81, 9, 81, 81, 3, 81, 81, 3, 81, 81, 9, 81, 81, 3, 81, 81, 1, 81, 81, 9, 81, 81, 1, 81, 81, 3, 81, 81, 9, 81, 81, 3, 81, 81, 3, 81, 81, 9, 81, 81, 3, 81, 81, 1, 81, 81, 9, 81, 81, 1, 81, 81, 3, 81, 81, 9, 81, 81, 3, 81, 81, 3, 81, 81, 9, 81, 81, 3, 81, 81, 1, 81, 81
Offset: 0

Views

Author

Paul Curtz, May 14 2010

Keywords

Comments

The generating formula is a(n) = A061040(n+3) - 9*A061039(n+3). This is a member of the family of sequences with A000012(n) = A000290(n+1) -A005563(n+1), with period length 1, and A177499(n) = A061038(n+2) -4*A061037(n+2), with period length 4.
a(n) here has period length 3^3 and the general series of this family has period length k^k.

Programs

  • PARI
    a(n)=3^[0, 4, 4, 1, 4, 4, 2, 4, 4, 1, 4, 4, 1, 4, 4, 2, 4, 4, 1, 4, 4, 0, 4, 4, 2, 4, 4][n%27+1] \\ Charles R Greathouse IV, Jul 17 2016

Formula

G.f.: ( -1 -81*x -3*x^9 -3*x^3 -81*x^4 -81*x^5 -9*x^6 -81*x^7 -81*x^8 -81*x^10 -3*x^12 -81*x^13 -81*x^14 -9*x^15 -81*x^16 -81*x^17 -3*x^18 -81*x^19 -81*x^20 -x^21 -81*x^22 -81*x^23 -9*x^24 -81*x^25 -81*x^26 -81*x^11 -81*x^2 ) / ( (x-1) *(1+x+x^2) *(1+x^3+x^6) *(1+x^9+x^18) ). - R. J. Mathar, Dec 09 2010
a(n) = a(n+27).
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