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Search: id:A100414
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| A100414 |
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Numbers n such that n is R(n)-th composite number where R(n) is the digit reversal of n (A002808(A004086(n))=n). |
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+0
2
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| 21, 48034, 69926, 180461, 214591, 409473, 563715, 41630193, 253385633342, 661494322636
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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There is no further term < 3*10^9.
a(11) > 3*10^12. [From Donovan Johnson (donovan.johnson(AT)yahoo.com), Jun 14 2009]
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EXAMPLE
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41630193 is in the sequence because 41630193 is 39103614-th composite number.
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MATHEMATICA
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Do[s=FromDigits[Reverse[IntegerDigits[n]]]; If[s<n&&!PrimeQ[n] &&s==n-PrimePi[n]-1, Print[n]], {n, 2, 42000000}]
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CROSSREFS
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Cf. A002808, A004086, A100412, A100413, A100415.
Sequence in context: A167063 A115485 A001167 this_sequence A068735 A013768 A143736
Adjacent sequences: A100411 A100412 A100413 this_sequence A100415 A100416 A100417
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KEYWORD
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base,more,nonn
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AUTHOR
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Farideh Firoozbakht (mymontain(AT)yahoo.com), Dec 10 2004
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EXTENSIONS
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a(9)-a(10) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Jun 14 2009
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