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 A361520 a(n) is the greatest prime factor of a(n-2)^2 + a(n-1)^2 where a(1)=2 and a(2)=3. 1
 2, 3, 13, 89, 809, 349, 409, 144541, 10446133981, 1361264878245241, 4398505263882824939701, 17847523009215848981, 512996953133650208042047593649109478833 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Sebastian F. Orellana, Table of n, a(n) for n = 1..15 MAPLE A[1]:= 2: A[2]:= 3: for n from 3 to 15 do A[n]:= max(numtheory:-factorset(A[n-2]^2 + A[n-1]^2)) od: seq(A[], n=1..15); # Robert Israel, Mar 17 2023 MATHEMATICA a[1] = 2; a[2] = 3; a[n_] := a[n] = FactorInteger[a[n - 1]^2 + a[n - 2]^2][[-1, 1]]; Array[a, 14] (* Amiram Eldar, Mar 14 2023 *) CROSSREFS Cf. A006530, A113494, A175723. Sequence in context: A212433 A013167 A224239 * A068096 A098462 A125283 Adjacent sequences: A361517 A361518 A361519 * A361521 A361522 A361523 KEYWORD nonn AUTHOR Sebastian F. Orellana, Mar 14 2023 STATUS approved

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Last modified October 2 10:57 EDT 2023. Contains 365833 sequences. (Running on oeis4.)