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A103163
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a(n) = gcd(reverse(prime(n)), reverse(prime(n+1))).
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1
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1, 1, 1, 1, 1, 1, 1, 1, 4, 1, 1, 1, 2, 2, 1, 5, 1, 4, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 14, 2, 2, 2, 4, 2, 2, 8, 2, 2, 2, 4, 2, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 13, 8, 2, 2, 2, 2, 2, 2, 8, 2, 2, 4, 4, 2, 2, 2, 2, 1, 5, 5, 25, 5, 5, 5, 5, 5, 5, 25, 5, 5, 5, 1, 2, 2, 4, 4, 4
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OFFSET
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1,9
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COMMENTS
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Greatest common divisor of two consecutive primes after each prime is written backward.
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LINKS
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FORMULA
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EXAMPLE
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Neither of these common divisors are divisible by 3 or by 10 or by 11.
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MAPLE
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p := ithprime(n) ;
q := nextprime(p) ;
igcd(digrev(p), digrev(q)) ;
end proc:
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MATHEMATICA
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rd[x_] :=FromDigits[Reversed[IntegerDigits[x]]]; Table[GCD[rd[Prime[w]], rd[Prime[w+1]]], {w, 1, 1000}]
GCD@@#&/@(Partition[IntegerReverse/@Prime[Range[120]], 2, 1]) (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jan 31 2020 *)
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CROSSREFS
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KEYWORD
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base,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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