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A242243

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

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

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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 &]