A117243 Chen numbers which are also twin primes.

3, 5, 7, 11, 13, 17, 19, 29, 31, 41, 59, 71, 101, 107, 109, 137, 139, 149, 179, 181, 191, 197, 199, 227, 239, 269, 281, 311, 347, 419, 431, 461, 521, 569, 571, 599, 617, 641, 659, 809, 811, 821, 827, 829, 857, 881, 1019, 1031, 1049, 1061, 1091, 1151, 1229

Offset: 1

Author

Jani Melik, Apr 22 2006

Keywords

• nonn

Examples

			(3, 5) are twin numbers and also Chen numbers.
		

Crossrefs

Cf. A001097, A109611.

Programs

Maple

ischenprime:=proc(n); if (isprime(n) = 'true') then if (isprime(n+2) = 'true' or numtheory[bigomega](n+2) = 2) then RETURN('true') else RETURN('false') fi fi end:
ts_chen_twin_primes:=proc(n) local i, ans; ans:=[ ]: for i from 1 to n do if (ischenprime(i) = 'true') and (isprime(i+2) = 'true' or isprime(i-2) = 'true') then ans:=[op(ans), i]: fi od; RETURN(ans) end:
ts_chen_twin_primes(1230);

Mathematica

Select[Prime[Range[250]],PrimeOmega[#+2]<3&&AnyTrue[#+{2,-2},PrimeQ]&] (* Harvey P. Dale, Jul 28 2023 *)

Extensions

Corrected and extended by Jani Melik, May 04 2013