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 A246943 a(4n) = 4*n , a(2n+1) = 8*n+4 , a(4n+2) = 2*n+1. 2
 0, 4, 1, 12, 4, 20, 3, 28, 8, 36, 5, 44, 12, 52, 7, 60, 16, 68, 9, 76, 20, 84, 11, 92, 24, 100, 13, 108, 28, 116, 15, 124, 32, 132, 17, 140, 36, 148, 19, 156, 40, 164, 21, 172, 44, 180, 23, 188, 48, 196, 25, 204, 52, 212, 27, 220, 56, 228 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Consider the denominators of the Balmer series A061038(n) = 0, 4, 1, 36, 16, 100,... (a permutation of the squares of the nonnegative numbers i.e. A000290(n)) divided by A028310(n)=1,1,2,... . The numerators are a(n). The denominators are A138191(n). Note that A061038(3n)=9*A061038(n), n>=1. a(3n) is divisible by the period 3 sequence: repeat 9, 3, 3. LINKS J. J. Balmer, Notiz über die Spectrallinien des Wasserstoffs, Annalen der Physik, vol. 261, 5 (1885) 80-87. First published June 25 1884 (Basel). Index entries for linear recurrences with constant coefficients, signature (0,0,0,2,0,0,0,-1). FORMULA Numerators of A061038(n)/A028310(n). a(2n) = A022998(n). G.f.: x*(4*x^6+x^5+12*x^4+4*x^3+12*x^2+x+4) / ((x-1)^2*(x+1)^2*(x^2+1)^2). - Colin Barker, Sep 08 2014 a(n) = n*(19-13*(-1)^n+(1+(-1)^n)*(-1)^((2*n-1+(-1)^n)/4))/8. - Luce ETIENNE, May 26 2015 a(n) = n*(19-(-1)^n*13+2*cos(n*Pi/2))/8. - Giovanni Resta, May 26 2015 EXAMPLE Numerators of a(0)=0/1=0, a(1)=4/1=4, a(2)=1/2, a(3)=36/3=12,... . MAPLE A246943:=n->n*(19-(-1)^n*13+2*cos(n*Pi/2))/8: seq(A246943(n), n=0..100); # Wesley Ivan Hurt, Apr 18 2017 PROG (PARI) concat(0, Vec(x*(4*x^6+x^5+12*x^4+4*x^3+12*x^2+x+4)/((x-1)^2*(x+1)^2*(x^2+1)^2) + O(x^100))) \\ Colin Barker, Sep 08 2014 CROSSREFS Cf. A145979, A138191, A061038, A028310, A022998. Sequence in context: A316232 A212046 A232013 * A106194 A272099 A329033 Adjacent sequences:  A246940 A246941 A246942 * A246944 A246945 A246946 KEYWORD nonn,easy AUTHOR Paul Curtz, Sep 08 2014 STATUS approved

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Last modified February 18 15:30 EST 2020. Contains 332019 sequences. (Running on oeis4.)