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A242243 Semiprimes sp of the form p^2 + q + 1 where p and q are consecutive primes. 1
15, 33, 187, 309, 559, 1411, 1897, 2263, 2869, 3543, 6979, 10717, 11559, 11995, 22353, 32953, 39009, 54529, 57363, 58333, 66313, 77011, 80383, 113917, 120759, 124969, 147079, 158011, 167701, 175983, 177673, 237661, 241581, 253519, 299767, 310813, 376387, 381309 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

K. D. Bajpai, Table of n, a(n) for n = 1..5970

EXAMPLE

a(1) = 15 = 3^2 + 5 + 1 = 3 * 5 is semiprime, 3 and 5 are consecutive primes.

a(2) = 33 = 5^2 + 7 + 1 = 3 * 11 is semiprime, 5 and 7 are consecutive primes.

MAPLE

with(numtheory): A242243:= proc()local k ; k:=(ithprime(x)^2+ithprime(x+1)+1); if  bigomega(k)=2 then RETURN (k); fi; end: seq(A242243 (), x=1..500);

MATHEMATICA

Select[Table[Prime[n]^2 + Prime[n + 1] + 1, {n, 500}], PrimeOmega[#] == 2 &]

CROSSREFS

Cf. A000040, A001358, A045636, A145292, A228183.

Sequence in context: A222179 A322493 A190052 * A219855 A270072 A085803

Adjacent sequences:  A242240 A242241 A242242 * A242244 A242245 A242246

KEYWORD

nonn

AUTHOR

K. D. Bajpai, May 09 2014

STATUS

approved

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Last modified July 24 03:01 EDT 2019. Contains 325290 sequences. (Running on oeis4.)