OFFSET
1,2
COMMENTS
This is likely a permutation of the positive integers.
a(2*n) is always a prime. - Sean A. Irvine, May 21 2019
a(2*n+1) is always a nonprime. - Sean A. Irvine, May 21 2019
LINKS
Carole Dubois, Table of n, a(n) for n = 1..1339
EXAMPLE
The sequence starts with 1,3,6,2,4,5,9,7,... and we see that:
a(1) + a(2) = 1 + 3 = 4 (nonprime sum of a nonprime and a prime);
a(2) + a(3) = 3 + 6 = 9 (nonprime sum of a prime and a nonprime);
a(3) + a(4) = 6 + 2 = 8 (nonprime sum of a nonprime and a prime);
a(4) + a(5) = 2 + 4 = 6 (nonprime sum of a prime and a nonprime);
a(5) + a(6) = 4 + 5 = 9 (nonprime sum of a nonprime and a prime); etc.
CROSSREFS
KEYWORD
nonn
AUTHOR
Carole Dubois and Eric Angelini, May 19 2019
STATUS
approved