OFFSET
0,2
COMMENTS
The upper branch visible in the scatterplot of the first terms corresponds to odd-indexed terms. - Rémy Sigrist, Jan 31 2018
LINKS
Rémy Sigrist, Table of n, a(n) for n = 0..10000
Rémy Sigrist, C++ program for A298990
EXAMPLE
2* 2 = 2 + 2, so a(1) = 2.
2* 4 = 3 + 5 = 5 + 3, so a(2) = 4.
2* 5 = 3 + 7 = 5 + 5 = 7 + 3, so a(3) = 5.
2* 8 = 3 + 13 = 5 + 11 = 11 + 5 = 13 + 3, so a(4) = 8.
2*11 = 3 + 19 = 5 + 17 = 11 + 11 = 17 + 5 = 19 + 3, so a(5) = 11.
PROG
(C++) See Links section.
(PARI) nb(n) = sum(i=1, 2*n-1, isprime(i) && isprime(2*n-i));
a(n) = {my(k=1); while (nb(k) != n, k++); k; } \\ Michel Marcus, Jan 31 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jan 31 2018
STATUS
approved