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 A242996 a(n) = (a(n-1)^2 - a(n-2)^4) * a(n-1) / a(n-2)^2 with a(1) = 1, a(2) = 2. 2
 1, 2, 6, 30, -330, 257070, 128005692870, 23279147893155496537470, 388475314992168993748220639081347493631827670 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS The next term (a(10)) has 90 digits and a(11) has 178 digits. - Harvey P. Dale, Feb 23 2023 LINKS G. C. Greubel, Table of n, a(n) for n = 1..13 FORMULA abs(a(n)) = A127815(n). a(n+1) = a(n) * A242995(n) for all n>0. 0 = a(n)^2*a(n+2) + a(n+1)*(a(n)^4 - a(n+1)^2) for all n>0. MATHEMATICA RecurrenceTable[{a[n] == (a[n-1]^2 - a[n-2]^4)*a[n-1]/a[n-2]^2, a[1] == 1, a[2] == 2}, a, {n, 1, 10}] (* G. C. Greubel, Aug 06 2018; corrected by Georg Fischer, Dec 07 2023 *) nxt[{a_, b_}]:={b, (b^2-a^4) b/a^2}; NestList[nxt, {1, 2}, 10][[;; , 1]] (* Harvey P. Dale, Feb 23 2023 *) PROG (PARI) {a(n) = if( n<3, max(0, n), my(x = a(n-2)^2, y = a(n-1)); (y^2 - x^2) * y / x)}; (Magma) I:=[1, 2]; [n le 2 select I[n] else (Self(n-1)^2 - Self(n-2)^2 )/Self(n-2)^2: n in [1..10]]; // G. C. Greubel, Aug 06 2018 CROSSREFS Cf. A127815, A242995. Sequence in context: A038696 A333373 A064847 * A127815 A054934 A001684 Adjacent sequences: A242993 A242994 A242995 * A242997 A242998 A242999 KEYWORD sign AUTHOR Michael Somos, Aug 17 2014 STATUS approved

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Last modified September 12 05:07 EDT 2024. Contains 375842 sequences. (Running on oeis4.)