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Search: id:A083991
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| 3, 7, 17, 29, 71, 83, 281, 719, 983, 997, 1637, 2309, 3701, 4493, 5507, 6299, 7691, 8363, 9161, 9803, 11003, 13163, 17117, 18371, 20807, 31181, 31793, 32693, 32843, 33617, 33893, 34211, 34673, 37277, 38453, 49409, 50591, 61547, 62723, 65327
(list; graph; listen)
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OFFSET
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1,1
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LINKS
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Diana Mecum, Table of n, a(n) for n = 1..341
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EXAMPLE
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Leading zeros are removed before concatenation: 997 is in here because 997 is in A083989 (9973 is prime) and its 10-complement 3 is also in A083989 (37 is prime). Unlike the example of 17 and 83, the 10-complement is not a 1-to-1 relation in cases where 9 shows up as a most significant digit.
17 and 83 both are members and are each other's 10's complement.
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MAPLE
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A055120 := proc(n) local digs ; digs := ilog10(n)+1 ; 10^digs-n ; end: isA083989 := proc(n) local comp, ccat ; if isprime(n) then comp := A055120(n) ; ccat := n*10^(ilog10(comp)+1)+comp ; RETURN( isprime(ccat)) ; else false ; fi ; end: isA083991 := proc(n) local comp; if isA083989(n) then comp := A055120(n) ; RETURN( isA083989(comp) ) ; else false ; fi ; end: for n from 1 to 80000 do if isA083991(n) then printf("%d, ", n) ; fi ; od ; - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 18 2007
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CROSSREFS
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Cf. A083989, A083990.
Sequence in context: A045424 A106968 A079779 this_sequence A006628 A068682 A045425
Adjacent sequences: A083988 A083989 A083990 this_sequence A083992 A083993 A083994
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KEYWORD
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base,nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), May 23 2003
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EXTENSIONS
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More terms from Diana Mecum (diana.mecum(AT)gmail.com) and R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 18 2007
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