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A242243 Semiprimes sp of the form p^2 + q + 1 where p and q are consecutive primes. 1

%I

%S 15,33,187,309,559,1411,1897,2263,2869,3543,6979,10717,11559,11995,

%T 22353,32953,39009,54529,57363,58333,66313,77011,80383,113917,120759,

%U 124969,147079,158011,167701,175983,177673,237661,241581,253519,299767,310813,376387,381309

%N Semiprimes sp of the form p^2 + q + 1 where p and q are consecutive primes.

%H K. D. Bajpai, <a href="/A242243/b242243.txt">Table of n, a(n) for n = 1..5970</a>

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

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

%p 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);

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

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

%K nonn

%O 1,1

%A _K. D. Bajpai_, May 09 2014

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Last modified July 27 02:39 EDT 2021. Contains 346302 sequences. (Running on oeis4.)