A024697 a(n) = p(1)p(n) + p(2)p(n-1) + ... + p(k)p(n+1-k), where k = [ (n+1)/2 ], p = A000040 = the primes.

4, 6, 19, 29, 68, 94, 177, 231, 400, 484, 753, 903, 1340, 1552, 2157, 2489, 3352, 3784, 5013, 5515, 7052, 7758, 9773, 10575, 13076, 14076, 17023, 18339, 21876, 23414, 27715, 29437, 34570, 36500, 42335, 44731, 51560, 54198, 61955, 65051, 73700, 77402, 87293

Offset

1,1

Comments

a(n) = A025129(n) for even n. - M. F. Hasler, Apr 06 2014

Links

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Maple

A024697:=n->sum( ithprime(k)*ithprime(n-k+1), k=1..(n+1)/2 ); seq(A024697(n), n=1..50); # Wesley Ivan Hurt, Apr 06 2014

Mathematica

Table[Sum[Prime[k] Prime[n - k + 1], {k, (n + 1)/2}], {n, 50}] (* Wesley Ivan Hurt, Apr 06 2014 *)

Prog

(PARI) A024697(n)=sum(k=1, (n+1)\2, prime(k)*prime(n-k+1)) \\ M. F. Hasler, Apr 06 2014
(Haskell)
a024697 n = a024697_list !! (n-1)
a024697_list = f (tail a000040_list) [head a000040_list] 2 where
   f (p:ps) qs k = sum (take (div k 2) $ zipWith (*) qs $ reverse qs) :
                   f ps (p : qs) (k + 1)
-- Reinhard Zumkeller, Apr 07 2014

Crossrefs

Cf. A014342, A000040.

Sequence in context: A013160 A153777 A034189 * A024874 A095383 A116383

Adjacent sequences: A024694 A024695 A024696 * A024698 A024699 A024700

Keyword

nonn

Author

Clark Kimberling

Extensions

Name edited and values double-checked by M. F. Hasler, Apr 06 2014

Status

approved