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Search: id:A156606
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| A156606 |
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a(n)=number of even digits in prime(n) + number of prime digits in prime(n). |
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+0
1
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| 2, 1, 1, 1, 0, 1, 1, 0, 3, 2, 1, 2, 1, 2, 2, 2, 1, 1, 2, 1, 2, 1, 2, 1, 1, 0, 1, 1, 0, 1, 3, 1, 2, 1, 1, 1, 2, 2, 2, 2, 1, 1, 0, 1, 1, 0, 2, 5, 5, 4, 4, 3, 3, 3, 4, 4, 3, 3, 4, 3, 4, 3, 2, 1, 2, 2, 2, 3, 3, 2, 3, 2, 3, 3, 2, 3, 2, 2, 1, 1, 1, 3, 2, 3, 2, 3, 2, 3, 2, 3, 3, 2, 3, 1, 1, 2, 1, 3, 4, 2, 3, 3, 3, 2, 2
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Even digits are 2, 4, 6 or 8 and prime digits are 2, 3, 5 or 7.
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EXAMPLE
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If prime(1)=2(even, prime), then 1+1=2=a(1). If prime(2)=3(0, prime), then 0+1=1=a(2). If prime(3)=5(0, prime), then 0+1+1=a(3). If prime(4)=7(0, prime), then 0+1=1+a(4). If prime(5)=11(0, 0), then 0+0=0=a(5), etc.
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MAPLE
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npris := proc(n) local dgs, a, i ; dgs := convert(n, base, 10) ; a := 0 ; for i in dgs do if isprime(i) then a := a+1 ; fi; od: a ; end: nevsnot0 := proc(n) local dgs, a, i ; dgs := convert(n, base, 10) ; a := 0 ; for i in dgs do if i mod 2 = 0 and i <> 0 then a := a+1 ; fi; od: a ; end: for n from 1 to 800 do p := ithprime(n) ; printf("%d, ", nevsnot0(p)+npris(p)) ; od: [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Feb 13 2009]
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CROSSREFS
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Cf. A000040.
Sequence in context: A037801 A053252 A117195 this_sequence A107034 A117410 A087810
Adjacent sequences: A156603 A156604 A156605 this_sequence A156607 A156608 A156609
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KEYWORD
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nonn
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AUTHOR
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Juri-Stepan Gerasimov (2stepan(ATrambler.ru), Feb 11 2009
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