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Search: id:A118496
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| A118496 |
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Reverse digits of largest Chen primes, append to sequence if result is larger Chen prime then previous one with reverse digits. |
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+0
1
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| 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; listen)
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OFFSET
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1,1
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COMMENT
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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.
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MAPLE
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# 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);
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CROSSREFS
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Cf. A004087, A098922, A109611.
Sequence in context: A004087 A118495 A028906 this_sequence A085300 A119388 A093487
Adjacent sequences: A118493 A118494 A118495 this_sequence A118497 A118498 A118499
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KEYWORD
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nonn,base,less
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AUTHOR
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Jani Melik (jani_melik(AT)hotmail.com), May 05 2006
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