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A338770 a(n) is the sum of primes of the form n - 2*p for primes p < n/2. 2
0, 0, 0, 0, 0, 2, 3, 2, 8, 0, 12, 2, 10, 0, 16, 2, 34, 0, 18, 0, 35, 0, 49, 2, 33, 0, 58, 2, 52, 0, 22, 0, 89, 0, 73, 2, 68, 0, 64, 2, 97, 0, 88, 0, 132, 0, 134, 2, 80, 0, 189, 0, 147, 0, 87, 0, 227, 0, 103, 2, 73, 0, 241, 2, 223, 0, 189, 0, 221, 0, 178, 0, 184, 0, 322, 2, 307, 0, 189, 0, 336, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,6

COMMENTS

If n is even then a(n)=2*A010051(n/2-1).

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

EXAMPLE

The representations of 31 as 2*p+q with p and q prime are 2*7+17 and 2*13+5, so a(31) = 17 + 5 = 22.

MAPLE

f:= proc(n) local q, v, t;

  t:= 0; q:= 1;

  do

    q:= nextprime(q);

    if 2*q > n then return t fi;

    v:= n - 2*q;

    if isprime(v) then t:= t+v fi;

  od;

end proc:

map(f, [$1..100]);

PROG

(PARI) a(n) = my(s=0); forprime(p=0, n\2, if (isprime(q=n-2*p), s+=q)); s; \\ Michel Marcus, Nov 08 2020

CROSSREFS

Cf. A010051.

Sequence in context: A048601 A008317 A139011 * A063708 A096488 A011280

Adjacent sequences:  A338767 A338768 A338769 * A338771 A338772 A338773

KEYWORD

nonn,look

AUTHOR

J. M. Bergot and Robert Israel, Nov 08 2020

STATUS

approved

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Last modified October 22 13:15 EDT 2021. Contains 348170 sequences. (Running on oeis4.)