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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
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified May 26 18:43 EDT 2017. Contains 287129 sequences.