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%I #8 Feb 27 2019 01:18:07
%S 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,
%T 17,13,19,11,23,17,19,7,31,17,23,19,23,13,31,17,29,19,29,19,31,23,29,
%U 23,31,19,37,17,41,29,31,19,43,23,41,29,37,31,37,29,41,31,41,31,43,29,47
%N List of pairs of primes that are equidistant from and nearest to n, or the pair (0,0) if there is no such pair.
%C Conjecture: There are only six 0's in this sequence.
%e Array begins:
%e n ............... Pair
%e 1 .............. 0 . 0
%e 2 .............. 0 . 0
%e 3 .............. 0 . 0
%e 4 .............. 3 . 5
%e 5 ............ 3 . . . 7
%e 6 .............. 5 . 7
%e 7 ........ 3 . . . . . . . 11
%e 8 .......... 5 . . . . . 11
%e 9 ............ 7 . . . 11
%e 10 ......... 7 . . . . . 13
%p 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
%Y Cf. A154720, A154721, A154722, A154723, A154724, A154725, A154726, A154727.
%K nonn,tabf
%O 1,7
%A _Omar E. Pol_, Jan 15 2009, Jan 18 2009
%E More terms from _R. J. Mathar_, Jul 13 2009
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