A118497 Primes that are not Chen primes written backwards.

34, 16, 37, 97, 79, 301, 151, 361, 371, 391, 322, 922, 142, 172, 772, 382, 313, 133, 943, 763, 373, 383, 793, 124, 334, 934, 754, 364, 325, 745, 395, 106, 706, 316, 916, 346, 166, 376, 196, 907, 727, 337, 937, 757, 377, 328, 358, 958, 388, 709, 929, 769, 799

Offset: 1

Author

Jani Melik, May 05 2006

Keywords

• nonn
• base
• less

Crossrefs

Cf. A004087, A102540, A109611.

Programs

Maple

# Check if number is Chen prime 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: #Reverse digits obrni_stev:=proc(n) local i, tren, tren1, st, ans; ans:=[ ]: tren:=n: tren1:=0: for i while (tren>0) do st:=round(10*frac(tren/10)): ans:=[op(ans), st]: tren:=trunc(tren/10): od: for i from 0 to nops(ans)-1 do tren1:= tren1 + op(nops(ans)-i, ans)*10^(i): od: return tren1 end: ts_inv_nonchen_pra:= proc(n) local i, trens, ans; trens:= [ ]; ans:=[ ]; for i from 1 to n do if (ischenprime( i ) = 'false') then ans:=[op(ans),obrni_stev(i)] fi: od: return ans end: ts_inv_nonchen_pra(2000);