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

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