A082094 - OEIS

A082094

A 2nd-order recursion: a(1)=a(2)=1; a(n) = prime(a(n-1)) + primepi(a(n-2)) = A000040(a(n-1)) + A000720(a(n-2)).

1, 1, 2, 3, 6, 15, 50, 235, 1498, 12592, 135431, 1806803, 29135476, 555971158, 12336554787, 313733168860, 9034347750986, 291579097035392, 10455240487002922, 413371595329570610

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OFFSET

1,3

LINKS

Table of n, a(n) for n=1..20.

MATHEMATICA

a[n_]:= a[n]= If[n<4, Fibonacci[n], Prime[a[n-1]] + PrimePi[a[n-2]]]; Table[a[n], {n, 1, 17}] (* modified by G. C. Greubel, Aug 31 2019 *)

PROG

(Magma) a:= func< n | n lt 4 select Fibonacci(n) else NthPrime(Self(n-1)) + #PrimesUpTo(Self(n-2)) >;

[a(n): n in [1..14]]; // G. C. Greubel, Aug 31 2019

CROSSREFS

Cf. A069103, A082095.

Sequence in context: A368954 A216144 A121688 * A320963 A061059 A060796

Adjacent sequences: A082091 A082092 A082093 * A082095 A082096 A082097

KEYWORD

nonn,more

AUTHOR

Labos Elemer, Apr 11 2003

EXTENSIONS

a(17) from G. C. Greubel, Aug 31 2019

a(18)-a(20) from Chai Wah Wu, Sep 18 2019

STATUS

approved