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A123342
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Least m such that 2^n+5^m is prime.
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2
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0, 0, 0, 1, 0, 1, 2, 5, 0, 5, 2, 1, 4, 3, 6, 11, 0, 19, 14, 3, 2, 5, 2, 3, 16, 11, 66, 35, 4, 7, 122, 17, 14, 13, 2, 3, 4, 15, 34, 52519, 4, 3, 22, 29, 10, 29, 6, 1, 4, 5, 38
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,7
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COMMENTS
| a(51) > 10^5
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EXAMPLE
| a(0)=0 because 2^0+5^0=1+1=2 is prime.
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MATHEMATICA
| f[n_] := Block[{p = If[n < 3 || EvenQ@n, 0, 1]}, While[ !PrimeQ[5^p + 2^n ], p += 2 ]; p] ; Table[f@n, {n, 0, 38}] (* Robert G. Wilson v *)
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PROG
| (PARI) for(n=0, 38, k=2^n; m=0; while(!isprime(k+5^m), m++); print1(m, ", ")) - (Klaus Brockhaus, Oct 15 2006)
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CROSSREFS
| Cf. A123252.
Sequence in context: A112695 A067881 A024714 * A196816 A058204 A090625
Adjacent sequences: A123339 A123340 A123341 * A123343 A123344 A123345
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KEYWORD
| nonn,hard,more
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AUTHOR
| Zak Seidov (zakseidov(AT)yahoo.com), Oct 11 2006
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EXTENSIONS
| Entries through a(38) checked by Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Oct 15 2006
a(40)-a(50) from Robert G. Wilson v (rgwv(AT)rgwv.com), Nov 14 2006
a(39)=52519 from Max Alekseyev (maxale(AT)gmail.com), Mar 15 2011
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