

A066875


Numbers n such that prime(n+1)+prime(n1)=2*prime(n).


3



3, 16, 37, 40, 47, 55, 56, 74, 103, 108, 111, 119, 130, 161, 165, 185, 188, 195, 200, 219, 240, 272, 273, 292, 340, 359, 388, 420, 427, 465, 466, 509, 521, 554, 600, 606, 622, 630, 634, 668, 683, 684, 703, 710, 711, 734, 762, 792, 814, 822, 823, 830, 831, 883
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OFFSET

1,1


COMMENTS

The indices of primes that are equidistant from the two primes surrounding them.  Harvey P. Dale, May 16 2013


LINKS

Harry J. Smith, Table of n, a(n) for n=1,...,1000


FORMULA

a(n) = PrimePi(A006562(n)).


MATHEMATICA

Select[Range[2, 1000], Prime[ # ] == (Prime[ # + 1] + Prime[ #  1])/2 &] (*Chandler*)
PrimePi/@Transpose[Select[Partition[Prime[Range[900]], 3, 1], Length[ Union[ Differences[ #]]]==1&]][[2]] (* Harvey P. Dale, May 16 2013 *)


PROG

(PARI) { n=0; for (m=2, 10^10, if (prime(m+1) + prime(m1) == 2*prime(m), write("b066875.txt", n++, " ", m); if (n==1000, return)) ) } [From Harry J. Smith, Apr 03 2010]


CROSSREFS

Sequence in context: A217130 A173390 A173891 * A196596 A196573 A196804
Adjacent sequences: A066872 A066873 A066874 * A066876 A066877 A066878


KEYWORD

nonn


AUTHOR

Benoit Cloitre, Jan 21 2002


EXTENSIONS

Corrected by Ray Chandler, Jan 09 2007


STATUS

approved



