A154800 List of pairs of primes that are equidistant from and nearest to n, or the pair (0,0) if there is no such pair.

0, 0, 0, 0, 0, 0, 3, 5, 3, 7, 5, 7, 3, 11, 5, 11, 7, 11, 7, 13, 5, 17, 11, 13, 7, 19, 11, 17, 13, 17, 13, 19, 11, 23, 17, 19, 7, 31, 17, 23, 19, 23, 13, 31, 17, 29, 19, 29, 19, 31, 23, 29, 23, 31, 19, 37, 17, 41, 29, 31, 19, 43, 23, 41, 29, 37, 31, 37, 29, 41, 31, 41, 31, 43, 29, 47

Offset

1,7

Comments

Conjecture: There are only six 0's in this sequence.

Links

Table of n, a(n) for n=1..76.

Example

Array begins:
n ............... Pair
1 .............. 0 . 0
2 .............. 0 . 0
3 .............. 0 . 0
4 .............. 3 . 5
5 ............ 3 . . . 7
6 .............. 5 . 7
7 ........ 3 . . . . . . . 11
8 .......... 5 . . . . . 11
9 ............ 7 . . . 11
10 ......... 7 . . . . . 13

Maple

A154800 := proc(n) local d; for d from 1 to n-1 do if isprime(n-d) and isprime(n+d) then printf("%d, %d, ", n-d, n+d); RETURN() ; fi; od: printf("0, 0, ") ; end: seq(A154800(n), n=1..80) ; # R. J. Mathar, Jul 13 2009

Crossrefs

Cf. A154720, A154721, A154722, A154723, A154724, A154725, A154726, A154727.

Sequence in context: A144294 A255313 A305883 * A263175 A137768 A137769

Adjacent sequences: A154797 A154798 A154799 * A154801 A154802 A154803

Keyword

nonn,tabf

Author

Omar E. Pol, Jan 15 2009, Jan 18 2009

Extensions

More terms from R. J. Mathar, Jul 13 2009

Status

approved