A118494 Palindromic primes that are not Chen primes.

151, 313, 373, 383, 727, 757, 929, 10501, 11311, 12421, 13831, 14341, 15451, 17971, 18181, 18481, 19391, 19891, 30103, 30203, 30403, 30703, 30803, 31513, 32323, 32423, 33533, 34543, 34843, 35053, 35153, 35353, 36563, 37273, 37573, 38083

Offset

1,1

Links

Table of n, a(n) for n=1..36.

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: # Check if number is palindrome ts_numpal:=proc(n) local ad; ad:=convert(n, base, 10): if (ListTools[Reverse](ad)=ad) then return 'true' else return 'false' fi end: ts_pal_nonchen:=proc(n) local i, ans; ans:=[ ]: for i from 1 to n do if (ischenprime(i) = 'false' and ts_numpal(i) = 'true') then ans:=[op(ans), i]: fi od: return ans end: ts_pal_nonchen(100000);

Mathematica

Select[ Prime[ Range[5000]], PalindromeQ [#]&&!PrimeQ[ # + 2] &&!PrimeOmega[ #+2]==2 &] (* James C. McMahon, Mar 29 2024 *)

Crossrefs

Cf. A002385, A109574, A109611.

Sequence in context: A142760 A142903 A031893 * A140022 A211551 A108842

Adjacent sequences: A118491 A118492 A118493 * A118495 A118496 A118497

Keyword

nonn,base,less

Author

Jani Melik, May 05 2006

Status

approved