A096453 - OEIS

A096453

Primes p such that the number of primes q, 5 <= q < p, congruent to 1 mod 3, is two less than the number of such primes congruent to 2 mod 3.

31, 59, 67, 73, 97, 103, 109, 127, 137, 149, 157, 179, 191, 197, 211, 241, 257, 347, 353, 379, 389, 401, 419, 431, 439, 449, 461, 467, 761, 773, 797, 1787, 1801, 1823, 1847, 1867, 1873, 1879, 1901, 3761, 9203, 198479, 198593

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OFFSET

1,1

LINKS

Table of n, a(n) for n=1..43.

MAPLE

ct := -2: q:=2: for n from 2 to 20000 do p:=q: q:=ithprime(n): ct:=ct+`if`(p mod 3 = 1, -1, 1): if(ct=2)then printf("%d, ", q): fi: od: # Nathaniel Johnston, Jun 16 2011

MATHEMATICA

npc1Q[n_]:=Module[{tot=PrimePi[n]-3, c}, c=Count[Prime[Range[3, tot+2]], _?(Mod[ #, 3]==1&)]; c==tot/2-1]; Select[Prime[Range[18000]], npc1Q] (* Harvey P. Dale, Aug 22 2013 *)

CROSSREFS

Cf. A096447-A096455.

Sequence in context: A220539 A193362 A293345 * A218794 A218771 A109356

Adjacent sequences: A096450 A096451 A096452 * A096454 A096455 A096456

KEYWORD

nonn,more

AUTHOR

Yasutoshi Kohmoto, Aug 12 2004

EXTENSIONS

More terms and better definition from Joshua Zucker, May 21 2006

STATUS

approved