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A118496 Reverse digits of largest Chen primes, append to sequence if result is larger Chen prime then previous one with reverse digits. 0
2, 3, 5, 7, 11, 31, 71, 101, 701, 941, 971, 991, 9001, 9011, 9221, 9521, 9941, 70001, 76001, 97001, 99401, 99431, 99571, 99989, 940001, 973001, 987101, 993401, 997811, 999431 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Although Chen primes are a subset of primes, this sequence is not a subset of A098922. The first number that is not member of the later is 9011.

LINKS

Table of n, a(n) for n=1..30.

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_prav_chen_pra:= proc(n) local i, tren, ans; tren:=0: ans:=[ ]: for i from 1 to n do if (ischenprime(i)='true' and ischenprime(obrni_stev(i))='true' and obrni_stev(i)>tren) then ans:=[op(ans), obrni_stev(i)]: tren:=obrni_stev(i): fi: od: return ans end: ts_inv_prav_chen_pra(200000);

CROSSREFS

Cf. A004087, A098922, A109611.

Sequence in context: A004087 A118495 A028906 * A085300 A119388 A093487

Adjacent sequences:  A118493 A118494 A118495 * A118497 A118498 A118499

KEYWORD

nonn,base,less

AUTHOR

Jani Melik, May 05 2006

STATUS

approved

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Last modified July 29 13:28 EDT 2021. Contains 346346 sequences. (Running on oeis4.)