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A061322 a(n) = a(n-1) * (1 + a(n-1)/n^2) with a(0) = 2. 1

%I

%S 2,6,15,40,140,924,24640,12415040,2408343949440,

%T 71606426901226335015040,51274803735606705472274088614112357905277056,

%U 21728144612603201307908899563300049012978385050783094682272184269369267136230071558272

%N a(n) = a(n-1) * (1 + a(n-1)/n^2) with a(0) = 2.

%C Only first 42 terms are integers (see A003504).

%F a(n) = a(n-1) + A003504(n+1)^2, a(n-1) = n * A003504(n+1). a(n) = A061314(2, n).

%e a(2) = 6 * (1 + 6/2^2) = 15.

%o (PARI) {a(n) = local(x); if( n<1, 2 * (n==0), (x = a(n-1)) + (x/n)^2)} /* _Michael Somos_, Apr 02 2006 */

%K nonn

%O 0,1

%A _Henry Bottomley_, Apr 24 2001

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Last modified September 17 03:42 EDT 2021. Contains 347478 sequences. (Running on oeis4.)