OFFSET
1,1
COMMENTS
Five together with primes that are the sum of two consecutive composite numbers.
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..10000
FORMULA
EXAMPLE
a(1)=1+4=5, a(2)=8+9=17.
MATHEMATICA
2*Select[Range[300], !PrimeQ[#] == !PrimeQ[#+1] && PrimeQ[2*#+1] &] + 1 (* G. C. Greubel, Jul 01 2016; Nov 10 2023 *)
PROG
(Magma) [2*n+1: n in [1..300] | (not IsPrime(n) eq not IsPrime(n+1)) and IsPrime(2*n+1)]; // G. C. Greubel, Nov 10 2023
(SageMath) [2*n+1 for n in (1..300) if (not is_prime(n)) - (not is_prime(n+1)) == 0 and is_prime(2*n+1)] # G. C. Greubel, Nov 10 2023
CROSSREFS
KEYWORD
nonn
AUTHOR
Juri-Stepan Gerasimov, Nov 15 2009
EXTENSIONS
Typo corrected and terms checked by D. S. McNeil, Nov 17 2010
STATUS
approved