A137781 a(n) = (2^prime(n) + 2^prime(n+1)) / 4.

3, 10, 40, 544, 2560, 34816, 163840, 2228224, 136314880, 671088640, 34896609280, 584115552256, 2748779069440, 37383395344384, 2286984185774080, 146366987889541120, 720575940379279360, 37469948899722526720, 627189298506124754944

Offset: 1

Author

Alexander R. Povolotsky, Apr 28 2008

Keywords

• nonn
• easy

Comments

Note that 4 is 2^prime(1).

Links

• G. C. Greubel, Table of n, a(n) for n = 1..460

Crossrefs

Cf. A034785, A137389.

Programs

Magma

[(2^NthPrime(n) + 2^NthPrime(n+1)) / 4: n in [1..20]]; // Vincenzo Librandi, Mar 28 2015

Maple

A137781:=n->(2^ithprime(n)+2^ithprime(n+1))/4: seq(A137781(n), n=1..20); # Wesley Ivan Hurt, Mar 27 2015

Mathematica

Table[(2^Prime[n] + 2^Prime[n + 1])/4, {n, 20}] (* Wesley Ivan Hurt, Mar 27 2015 *)
(2^#[[1]]+2^#[[2]])/4&/@Partition[Prime[Range[20]],2,1] (* Harvey P. Dale, Dec 21 2019 *)

PARI

vector(15,n,(2^prime(n)+2^prime(n+1))/4) \\ Derek Orr, Mar 29 2015

Formula

From Wesley Ivan Hurt, Mar 27 2015: (Start)

a(n) = A137389(n)/4.

a(n) = (A034785(n) + A034785(n+1))/4. (End)