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A242218 Semiprimes which are the arithmetic mean of three consecutive primes. 1
511, 537, 1073, 1461, 1501, 1541, 1763, 2071, 2181, 2449, 4101, 4387, 4399, 4467, 4559, 4607, 4681, 4705, 5089, 5257, 5429, 6415, 6621, 6671, 7097, 7111, 7261, 7391, 7447, 7811, 7831, 7897, 7909, 7969, 8079, 8129, 8193, 8333, 8639, 8915, 9101, 9113, 9123, 9211 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

K. D. Bajpai, Table of n, a(n) for n = 1..10000

EXAMPLE

a(1) = 511 = (503 + 509 + 521)/3 = 7 * 73 is semiprime.

a(2) = 537 = (523 + 541 + 547)/3 = 3 * 179 is semiprime.

MAPLE

with(numtheory): A242218:= proc()local k ; k:=(ithprime(x)+ithprime(x+1)+ithprime(x+2))/3; if k=floor(k) and bigomega(k)=2 then RETURN (k);  fi; end: seq(A242218 (), x=2..2000);

PROG

(PARI) for(k=1, 2000, t=prime(k)+prime(k+1)+prime(k+2); if(t%3==0 && bigomega(t/3)==2, print1(t/3, ", "))) \\ Colin Barker, May 08 2014

CROSSREFS

Cf. A001358, A133529, A216432, A234297.

Sequence in context: A196289 A027494 A145588 * A051985 A103206 A277172

Adjacent sequences:  A242215 A242216 A242217 * A242219 A242220 A242221

KEYWORD

nonn

AUTHOR

K. D. Bajpai, May 07 2014

STATUS

approved

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Last modified February 26 17:19 EST 2020. Contains 332293 sequences. (Running on oeis4.)