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 A171522 Denominator of 1/n^2-1/(n+2)^2. 8
 0, 9, 16, 225, 144, 1225, 576, 3969, 1600, 9801, 3600, 20449, 7056, 38025, 12544, 65025, 20736, 104329, 32400, 159201, 48400, 233289, 69696, 330625, 97344, 455625, 132496, 613089, 176400, 808201, 230400, 1046529, 295936, 1334025, 374544, 1677025, 467856 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS This is the third column in the table of denominators of the hydrogenic spectra (the main diagonal A147560): 0,   0,   0,   0,   0,   0,   0,   0... A000004 1,   4,   9,  16,  25,  36,  49,  64... A000290 1,  36,  16, 100,   9, 196,  64, 324... A061038 1, 144, 225,  12, 441, 576,  81, 900... A061040 1, 400, 144, 784,  64,1296, 400,1936... A061042 1, 900 1225,1600,2025, 100,3025,3600... A061044 1,1764, 576, 324, 225,4356,  48,6084... A061046 1,3136,3969,4900,5929,7056,8281, 196... A061048. LINKS Colin Barker, Table of n, a(n) for n = 0..1000 Index entries for linear recurrences with constant coefficients, signature (0,5,0,-10,0,10,0,-5,0,1). FORMULA a(n) = (A066830(n+1))^2. a(n) = -((-5+3*(-1)^n)*n^2*(2+n)^2)/8. - Colin Barker, Nov 05 2014 G.f.: x*(x^8+4*x^6+16*x^5+190*x^4+64*x^3+180*x^2+16*x+9) / ((x-1)^5*-(x+1)^5). - Colin Barker, Nov 05 2014 MAPLE A171522 := proc(n) if n = 0 then 0 else lcm(n+2, n) ; %^2 ; end if ; end: seq(A171522(n), n=0..70) ; # R. J. Mathar, Dec 15 2009 MATHEMATICA a[n_] := If[EvenQ[n], (n*(n+2))^2/4, (n*(n+2))^2]; Table[a[n], {n, 0, 36}] (* Jean-François Alcover, Jun 13 2017 *) PROG (PARI) concat(0, Vec(x*(x^8+4*x^6+16*x^5+190*x^4+64*x^3+180*x^2+16*x+9) / ((x-1)^5*-(x+1)^5) + O(x^100))) \\ Colin Barker, Nov 05 2014 CROSSREFS Cf. A105371. Bisections: A060300, A069075. Sequence in context: A075373 A072470 A053911 * A236287 A050802 A264519 Adjacent sequences:  A171519 A171520 A171521 * A171523 A171524 A171525 KEYWORD nonn,easy,frac AUTHOR Paul Curtz, Dec 11 2009 EXTENSIONS Edited and extended by R. J. Mathar, Dec 15 2009 STATUS approved

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Last modified October 17 06:08 EDT 2019. Contains 328106 sequences. (Running on oeis4.)