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 A183893 Real part of a Gaussian integer sequence with a Gaussian integer Somos-4 Hankel transform. 4
 1, 1, -1, -1, 9, 9, -73, -73, 697, 697, -7161, -7161, 77457, 77457, -868881, -868881, 10016241, 10016241, -117935473, -117935473, 1412307481, 1412307481, -17148100569, -17148100569, 210619695913, 210619695913, -2612194773481, -2612194773481, 32668519882017, 32668519882017, -411515480555553 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,5 COMMENTS Hankel transform of A183893(n)+I*A183894(n) is the (-4,-4) Somos-4 Gaussian integer sequence A183895(n)+I*A183896(n). LINKS G. C. Greubel, Table of n, a(n) for n = 0..500 FORMULA a(n) = Re(Sum{k=0..n, C(floor((n+k)/2),k)*I^k*A000108(k)}), I=sqrt(-1). MATHEMATICA Table[Re[Sum[I^k*Binomial[2*k, k]*Binomial[Floor[(n + k)/2], k]/(k + 1), {k, 0, n}]], {n, 0, 50}] (* G. C. Greubel, Feb 21 2018 *) PROG (PARI) for(n=0, 50, print1(real(sum(k=0, n, I^k*binomial(2*k, k)* binomial( floor((n+k)/2), k)/(k+1) )), ", ")) \\ G. C. Greubel, Feb 21 2018 (MAGMA) [Round(Real((&+[(Sqrt(-1))^k*Binomial(2*k, k)*Binomial( Floor((n+k)/2), k)/(k+1): k in [0..n]]))): n in [0..30]]; // G. C. Greubel, Feb 21 2018 CROSSREFS Sequence in context: A243125 A270008 A255743 * A210052 A239225 A165830 Adjacent sequences:  A183890 A183891 A183892 * A183894 A183895 A183896 KEYWORD sign AUTHOR Paul Barry, Jan 07 2011 STATUS approved

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Last modified December 4 15:16 EST 2020. Contains 338927 sequences. (Running on oeis4.)