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A118495 Chen primes written backwards. 0
2, 3, 5, 7, 11, 31, 71, 91, 32, 92, 13, 73, 14, 74, 35, 95, 76, 17, 38, 98, 101, 701, 901, 311, 721, 131, 731, 931, 941, 751, 761, 971, 181, 191, 791, 991, 112, 722, 332, 932, 152, 752, 362, 962, 182, 392, 703, 113, 713, 733, 743, 353, 953, 973, 983, 104, 904 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..57.

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_chen_pra:= proc(n) local i, trens, ans; trens:= [ ]; ans:=[ ]; for i from 1 to n do if (ischenprime( i ) = 'true') then ans:=[op(ans), obrni_stev(i)] fi: od: return ans end: ts_inv_chen_pra(2000);

MATHEMATICA

psp=Take[Union[Join[Union[Times@@@Tuples[Prime[Range[100]], {2}]], Prime[Range[PrimePi[250000]]]]], 200];

FromDigits[Reverse[IntegerDigits[#]]]&/@(Select[Prime[Range[PrimePi[1000]]], MemberQ[psp, #+2]&])  (* Harvey P. Dale, Feb 08 2011 *)

CROSSREFS

Cf. A004087, A109611.

Sequence in context: A098922 A265324 A004087 * A028906 A118496 A085300

Adjacent sequences:  A118492 A118493 A118494 * A118496 A118497 A118498

KEYWORD

nonn,base,less

AUTHOR

Jani Melik, May 05 2006

STATUS

approved

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Last modified August 5 00:15 EDT 2021. Contains 346456 sequences. (Running on oeis4.)