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A281660 The least common multiple of 1+n and 1+n^2. 3

%I

%S 1,2,15,20,85,78,259,200,585,410,1111,732,1885,1190,2955,1808,4369,

%T 2610,6175,3620,8421,4862,11155,6360,14425,8138,18279,10220,22765,

%U 12630,27931,15392,33825,18530,40495,22068,47989,26030,56355,30440,65641,35322

%N The least common multiple of 1+n and 1+n^2.

%H Colin Barker, <a href="/A281660/b281660.txt">Table of n, a(n) for n = 0..1000</a>

%H <a href="/index/Rec#order_08">Index entries for linear recurrences with constant coefficients</a>, signature (0,4,0,-6,0,4,0,-1)

%F a(n) = lcm(1+n,1+n^2) = (1+n)*(1+n^2)/gcd(1+n,1+n^2) = A053698(n)/A000034(n).

%F G.f.: (5*x^2+1) *(x^4+2*x^3+6*x^2+2*x+1) / ( (x-1)^4 *(1+x)^4 ).

%F a(2*n+1) = 2*A059722(n+1). - _R. J. Mathar_, Jan 28 2017

%F a(n) = ((3 + (-1)^n)*(1+n+n^2+n^3)) / 4. - _Colin Barker_, Feb 07 2017

%p A281660 := proc(n)

%p ilcm(1+n,1+n^2) ;

%p end proc:

%K nonn,easy

%O 0,2

%A _R. J. Mathar_, Jan 26 2017

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Last modified June 6 04:15 EDT 2020. Contains 334859 sequences. (Running on oeis4.)