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Search: id:A098922
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| A098922 |
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Reverse digits of largest primes, append to sequence if result is larger prime then previous one with reverse digits. |
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+0
2
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| 2, 3, 5, 7, 11, 31, 71, 73, 97, 101, 701, 941, 971, 991, 9001, 9601, 9721, 9931, 9941, 9967, 70001, 90001, 93001, 96001, 97001, 99401, 99611, 99721, 99881, 99923, 99989, 940001, 972001, 973001, 996001, 997001, 999101, 999331, 999431, 999631, 999931
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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The prime 37 in reverse is 73. 73 is prime and is larger than previous prime (17), written with reverse digits 71.
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MAPLE
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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_pra:= proc(n) local i, tren, ans; tren:=0: ans:=[ ]: for i from 1 to n do if ( isprime( i ) = 'true' and isprime( 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_pra(200000);
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CROSSREFS
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Cf. A004087, A095180.
Sequence in context: A119834 A095180 A101989 this_sequence A004087 A118495 A028906
Adjacent sequences: A098919 A098920 A098921 this_sequence A098923 A098924 A098925
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KEYWORD
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base,easy,nonn
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AUTHOR
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Jani Melik (jani_melik(AT)hotmail.com), Oct 18 2004
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