OFFSET
1,3
COMMENTS
2*prime(n) = A100484(n), the n-th even semiprime.
a(n) = A071681(n) + 1. - Reinhard Zumkeller, Mar 27 2015
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
EXAMPLE
2*prime(23) = 166 can be represented in 6 ways as the unordered sum of two primes: 166 = 3+163 = 17+149 = 29+137 = 53+113 = 59+107 = 83+83, so a(23) = 6.
2*prime(54) = 502 can be represented in 15 ways as the unordered sum of two primes: 502 = 3+499 = 11+491 = 23+479 = 41+461 = 53+449 = 59+443 = 71+431 = 83+419 = 101+401 = 113+389 = 149+353 = 191+311 = 233+269 = 239+263 = 251+251, so a(54) = 15.
PROG
(PARI) {for(n=1, 83, c=0; k=2*prime(n); forprime(p=2, prime(n), if(isprime(k-p), c++)); print1(c, ", "))} - Klaus Brockhaus, Dec 23 2006
(Haskell)
a116619 = (+ 1) . a071681 -- Reinhard Zumkeller, Mar 27 2015
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Jonathan Vos Post, Mar 14 2006
EXTENSIONS
Edited, corrected and extended by Klaus Brockhaus, Dec 23 2006
STATUS
approved