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Search: id:A154522
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| A154522 |
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Numbers n such that number of identical and smallest digits in prime(n) = 2. |
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+0
1
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| 5, 30, 32, 36, 42, 43, 47, 48, 49, 50, 64, 68, 71, 74, 76, 84, 87, 102, 130, 138, 139, 141, 151, 156, 165, 169, 188, 189, 191, 192, 195, 196, 198, 199, 202, 210, 215, 216, 218, 221, 230, 233, 234, 242, 248, 255, 256, 257, 268, 271, 282, 284, 286, 293, 294, 297
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Indices n such that the smallest digit in prime(n), A060420(n), appears twice in the decimal representation of prime(n). [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jan 12 2009]
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EXAMPLE
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If 191=prime(n=43), 1=1 and 1<9, the 43=a(6). If 199=prime(n=45), then 9=9 and 9>1. If 211=prime(n=47), 1=1 and 1<2, then 47=a(7). If 223=prime(n=48), 2=2 and 2<3, then 48=a(48), etc.
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MAPLE
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A060420 := proc(n) convert(ithprime(n), base, 10) ; min(op(%)) ; end: dcount := proc(di, n) local a, d; a := 0 ; convert(n, base, 10) ; for d in % do if d = di then a := a+1 ; fi; od; a ; end: isA154522 := proc(n) local d, c ; d := A060420(n) ; c := dcount(d, ithprime(n)) ; RETURN( c = 2 ) ; end: for n from 1 to 800 do if isA154522(n) then printf("%d, ", n) ; fi; od: [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jan 12 2009]
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CROSSREFS
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Cf. A000040.
Sequence in context: A056869 A098346 A134166 this_sequence A097252 A043886 A044463
Adjacent sequences: A154519 A154520 A154521 this_sequence A154523 A154524 A154525
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KEYWORD
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nonn,base,uned
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AUTHOR
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Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Jan 11 2009
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EXTENSIONS
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Removed 205, 206, 208. Added 210. R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jan 12 2009
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