[seqfan] a(n)+a(a(n)) is prime
Eric Angelini
Eric.Angelini at kntv.be
Sat Apr 11 15:40:18 CEST 2015
Hello SeqFans,
S is the lexicographically first seq where a(n)+a(a(n)) is prime.
[This is not http://oeis.org/A083569
as the integers 4, 17, etc. will never
appear here].
S=1,3,2,5,6,7,10,9,8,13,12,11,16,15,14,21,18,19,22,23,20,26,24,...
Example:
1 + (the 1st integer of S) is prime (1+1=2)
3 + (the 3rd integer of S) is prime (3+2=5)
2 + (the 2nd integer of S) is prime (2+3=5)
5 + (the 5th integer of S) is prime (5+6=11)
6 + (the 6th integer of S) is prime (6+7=13)
7 + (the 7th integer of S) is prime (7+10=17)
10 + (the 10th integer of S) is prime (10+13=23)
9 + (the 9th integer of S) is prime (9+8=17)
8 + (the 8th integer of S) is prime (8+9=17)
etc.
S is always extended with the smallest
integer not yet in S and not leading
to a contradiction.
Best,
É.
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