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Search: id:A156343
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| A156343 |
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Primes with equal number of prime and nonprime digits. |
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+0
1
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| 13, 17, 29, 31, 43, 47, 59, 67, 71, 79, 83, 97, 1033, 1123, 1153, 1213, 1217, 1229, 1231, 1259, 1279, 1283, 1297, 1303, 1307, 1321, 1367, 1423, 1427, 1433, 1453, 1531, 1543, 1559, 1567, 1571, 1579, 1583, 1597, 1627, 1637, 1657, 1721, 1747, 1759, 1783, 1787
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Prime digits are 2, 3, 5 or 7. Nonprime digits are 0, 1, 4, 6, 8 or 9.
Complement of (A154385 U A154386). [Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Nov 29 2009]
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EXAMPLE
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13(1=nonprime and 3=prime)=a(1).
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MAPLE
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A109066c := proc(n) nops(convert(n, base, 10))-A109066(n) ; end:
A109066 := proc(n) local dgs, a ; dgs := convert(n, base, 10) ; a := 0 ; for i in dgs do if isprime(i) then a := a+1 ; fi; od: a ; end:
for i from 1 to 400 do p := ithprime(i) ; if A109066(p) = A109066c(p) then printf("%d, ", p) ; fi; od: [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Feb 09 2009]
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CROSSREFS
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Cf. A000040.
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KEYWORD
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nonn,base,new
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AUTHOR
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Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Feb 08 2009
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