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A130130 a(0)=0, a(1)=1, a(n)=2 for n >= 2. 18

%I

%S 0,1,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,

%T 2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,

%U 2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2

%N a(0)=0, a(1)=1, a(n)=2 for n >= 2.

%C a(n) is also total number of positive integers below 10^(n+1) requiring 9 positive cubes in their representation as sum of cubes (cf. Dickson, 1939).

%C A061439(n) + A181375(n) + A181377(n) + A181379(n) + A181381(n) + A181400(n) + A181402(n) + A181404(n) + a(n) = A002283(n).

%C a(n) = number of obvious divisors of n. The obvious divisors of n are the numbers 1 and n. - _Jaroslav Krizek_, Mar 02 2009

%C Number of colors needed to paint n adjacent segments on a line. - _Jaume Oliver Lafont_, Mar 20 2009

%C a(n) = ceiling(n-th nonprimes/n) = ceiling(A018252(n)/A000027(n)) for n >= 1. Numerators of (A018252(n)/A000027(n)) in A171529(n), denominators of (A018252(n)/A000027(n)) in A171530(n). a(n) = A171624(n) + 1 for n >= 5. - _Jaroslav Krizek_, Dec 13 2009

%C a(n) is also the continued fraction for sqrt(1/2). - _Enrique Pérez Herrero_, Jul 12 2010

%C For n >= 1, a(n) = minimal number of divisors of any n-digit number. See A066150 for maximal number of divisors of any n-digit number. - _Jaroslav Krizek_, Jul 18 2010

%C Central terms in the triangle A051010. - _Reinhard Zumkeller_, Jun 27 2013

%H Leonard Eugene Dickson, <a href="http://projecteuclid.org/euclid.bams/1183502007">All integers except 23 and 239 are sums of eight cubes</a>, Bulletin of the American Mathematical Society 45 (1939), p. 588-591.

%H Eric W. Weisstein, <a href="http://mathworld.wolfram.com/WaringsProblem.html">MathWorld -- Waring's Problem.</a>

%H <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (1).

%F a(n) = 2*[(n+2) mod (n+1)] - [n!^2 mod (n+1)]*[(n+1)!^2 mod (n+2)], with n>=0. - _Paolo P. Lava_, Aug 28 2007

%F G.f.: x*(1+x)/(1-x)=x*(1-x^2)/(1-x)^2. - _Jaume Oliver Lafont_, Mar 20 2009

%F a(n) = A000005(n) - A070824(n) for n >= 1.

%t A130130[0]:=0; A130130[1]:=1; A130130[n_]:=2; (* _Enrique Pérez Herrero_, Jul 12 2010 *)

%t A130130[n_]:=ContinuedFraction[Sqrt[1/2],n+1][[n+1]] (* _Enrique Pérez Herrero_, Jul 12 2010 *)

%t Join[{0, 1},LinearRecurrence[{1},{2},96]] (* _Ray Chandler_, Sep 23 2015 *)

%o (PARI) a(n)=min(n,2) \\ _Charles R Greathouse IV_, Jun 01 2011

%o (Haskell)

%o a130130 = min 2

%o a130130_list = 0 : 1 : repeat 2 -- _Reinhard Zumkeller_, Jun 27 2013

%Y Cf. A158411. - _Jaume Oliver Lafont_, Mar 20 2009

%K nonn,easy

%O 0,3

%A _Paul Curtz_, Aug 01 2007

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Last modified March 26 20:47 EDT 2019. Contains 321535 sequences. (Running on oeis4.)