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Search: id:A145387
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| A145387 |
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Natural numbers n such that n-1 and n+1 are prime, also (sum of digits) + 1 and (sum of digits) - 1 is prime. |
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+0
1
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| 4, 6, 42, 60, 138, 150, 192, 198, 228, 240, 282, 312, 420, 462, 570, 600, 642, 660, 822, 828, 882, 1032, 1050, 1092, 1230, 1278, 1290, 1302, 1320, 1452, 1722, 1872, 2028, 2082, 2088, 2112, 2130, 2268, 2310, 2550, 2592, 2712, 2730, 2790, 2802, 2970, 3120
(list; graph; listen)
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OFFSET
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1,1
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MAPLE
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isA0145745 := proc(n) RETURN( isprime(n-1) and isprime(n+1)) ; end: A007953 := proc(n) add(i, i=convert(n, base, 10) ); end: isA145387 := proc(n) RETURN(isA0145745(n) and isprime( A007953(n)+1) and isprime( A007953(n)-1) ) ; end: for n from 1 to 3400 do if isA145387(n) then printf("%d, ", n) ; fi; od: [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Nov 18 2008]
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CROSSREFS
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Cf. A014574.
Sequence in context: A074061 A125081 A023644 this_sequence A034923 A013022 A012908
Adjacent sequences: A145384 A145385 A145386 this_sequence A145388 A145389 A145390
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KEYWORD
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base,easy,nonn
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AUTHOR
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Giovanni Teofilatto (g.teofilatto(AT)tiscalinet.it), Oct 10 2008
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EXTENSIONS
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198 inserted by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Nov 18 2008
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