A167486 Choose the prime sum of pair (n,n+1) otherwise choose n (see comments for details).

3, 7, 11, 7, 17, 10, 23, 13, 29, 16, 17, 37, 41, 22, 47, 25, 53, 28, 59, 31, 32, 67, 71, 37, 38, 79, 83, 43, 89, 46, 47, 97, 101, 52, 107, 55, 113, 58, 59, 60, 61, 62, 127, 131, 67, 137, 70, 71, 72, 73, 149, 76, 77, 157, 80, 163, 167, 85, 173, 88, 179, 91, 92, 93, 94, 191

Offset

1,1

Comments

We start with the sequence of natural numbers A000027:

1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,...

Consider the first pair (1,2), it sums to prime, 3, hence a(1)=3, and we consider the next pair (3,4), again 3+4=7 is prime hence a(2)=7; and also, 5+6=11 is prime hence a(3)=11; now the next pair (7,8) sums to 15 which is not prime, hence a(4)=7, and next pair under consideration is (8,9) which gives a(5)=8+9=17; 10+11 is not pair hence a(6)=10; 11+12=23 is prime hence a(7)=23, etc.

In short, if the current pair sums to prime we take this sum as the next term of the sequence, otherwise the lesser member of pair is taken as the next term of the sequence.

Links

Table of n, a(n) for n=1..66.

Mathematica

n=1; s=Reap[Do[If[PrimeQ[p=2n+1], b=p; n=n+2, b=n; n=n+1]; Sow[b], {20}]][[2, 1]]

Crossrefs

Sequence in context: A093931 A335980 A153788 * A260408 A261103 A262505

Adjacent sequences: A167483 A167484 A167485 * A167487 A167488 A167489

Keyword

nonn

Author

Zak Seidov, Nov 04 2009

Status

approved