A104485 Primes p = p(k) such that prime(k) + 2 and prime(k+1) + 2 are both semiprimes.

19, 31, 47, 83, 109, 113, 127, 199, 251, 257, 293, 353, 401, 443, 467, 479, 487, 491, 499, 503, 557, 571, 577, 647, 677, 743, 761, 787, 829, 863, 911, 937, 941, 947, 971, 977, 983, 1109, 1187, 1193, 1291, 1327, 1361, 1381, 1399, 1459, 1499, 1553, 1559

Offset: 1

Author

Giovanni Teofilatto, Apr 19 2005

Keywords

• easy
• nonn

Examples

			19 is a term because prime(8) + 2 = 19 + 2 = 21 = 3*7 and prime(9) + 2 = 25 = 5*5.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A063637.

Programs

Mathematica

fQ[n_] := Plus @@ Flatten[ Table[ #[[2]], {1}] & /@ FactorInteger[n]] == 2; Prime /@ Select[ Range[ 270], fQ[ Prime[ # ] + 2] && fQ[ Prime[ # + 1] + 2] &] (* Robert G. Wilson v, Apr 19 2005 *)
Select[Prime[Range[250]],PrimeOmega[#+2]==PrimeOmega[NextPrime[#]+2]==2&] (* Harvey P. Dale, Apr 01 2024 *)

Extensions

Corrected and extended by Robert G. Wilson v, Apr 19 2005