OFFSET
1,1
COMMENTS
LINKS
K. D. Bajpai, Table of n, a(n) for n = 1..5000
EXAMPLE
a(1) = 8 is a term because 2*8 + 3 = 19 is a prime; but 4*8 + 3 = 35 = (5*7) is a composite number.
a(4) = 16 is a term because 2*16 + 3 = 35 = (5*7) is a composite number; but 4*16 + 3 = 67 is a prime.
a(6) = 26 is a term because 2*26 + 3 = 55 = (5*11) is a composite number; but 4*26 + 3 = 107 is a prime.
MATHEMATICA
Select[Range[0, 250], Xor[PrimeQ[2 # + 3], PrimeQ[4 # + 3]] &]
Select[Range[200], Total[Boole[PrimeQ[{2, 4}#+3]]]==1&] (* Harvey P. Dale, Jan 26 2023 *)
PROG
(PARI) isok(k) = bitxor(isprime(2*k+3), isprime(4*k+3)); \\ Michel Marcus, Aug 29 2020
CROSSREFS
KEYWORD
nonn
AUTHOR
K. D. Bajpai, Aug 29 2020
STATUS
approved