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A093940
Primes of the form 4*10^k + 7*R_k, where R_k is the repunit (A002275) of length k.
1
47, 47777, 47777777777777, 47777777777777777777777777, 4777777777777777777777777777777777777
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OFFSET
1,1
COMMENTS
The next term has 358 digits. - Harvey P. Dale, Nov 13 2013
LINKS
Table of n, a(n) for n=1..5.
Makoto Kamada, Prime numbers of the form 477...77.
Index entries for primes involving repunits.
MATHEMATICA
Select[Table[FromDigits[PadRight[{4}, n, 7]], {n, 500}], PrimeQ] (* Harvey P. Dale, Nov 13 2013 *)
CROSSREFS
Cf. A002275, A056708 (corresponding k).
Sequence in context: A287225 A033520 A210818 * A237512 A224468 A353697
Adjacent sequences: A093937 A093938 A093939 * A093941 A093942 A093943
KEYWORD
nonn
AUTHOR
Rick L. Shepherd, Apr 17 2004
STATUS
approved

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Last modified October 6 16:13 EDT 2024. Contains 376579 sequences.
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