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 A178377 A (-1,-3) Somos-4 sequence associated to y^2 + y = x^3 + 4*x^2 + x. 2
 1, 1, -3, -5, -22, -141, 719, 8765, 14319, 1707596, -21672017, -962616165, 16392942967, -1419903481091, 100267906812546, 7990790144939605, -1147738310571578779, 53860607055523082151, -43705893899966302362943 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS Hankel transform of the sequence with g.f. 1/(1-x/(1+3x^2/(1+(5/9)x^2/91-(66/25)x^2/(1-..., where -3,-5/9,66/25,... are the x-coordinates of the multiples of (0,0). LINKS G. C. Greubel, Table of n, a(n) for n = 0..124 FORMULA a(n) = (-a(n-1)*a(n-3) - 3*a(n-2)^2)/a(n-4), n>3. MATHEMATICA RecurrenceTable[{a[n]==(-a[n-1]*a[n-3] -3*a[n-2]^2)/a[n-4], a[0] == 1, a[1] == 1, a[2] == -3, a[3] == -5}, a, {n, 0, 30}] (* G. C. Greubel, Sep 16 2018 *) PROG (PARI) m=30; v=concat([1, 1, -3, -5], vector(m-4)); for(n=5, m, v[n] = ( -v[n-1]*v[n-3] - 3*v[n-2]^2)/v[n-4]); v \\ G. C. Greubel, Sep 16 2018 (Magma) I:=[1, 1, -3, -5]; [n le 4 select I[n] else (-Self(n-1)*Self(n-3) - 3*Self(n-2)^2)/Self(n-4): n in [1..30]]; // G. C. Greubel, Sep 16 2018 CROSSREFS Sequence in context: A124423 A209109 A212260 * A270621 A270637 A064187 Adjacent sequences: A178374 A178375 A178376 * A178378 A178379 A178380 KEYWORD easy,sign AUTHOR Paul Barry, May 26 2010 STATUS approved

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Last modified August 9 11:18 EDT 2024. Contains 375041 sequences. (Running on oeis4.)