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A093174
Primes of the form 40*R_k + 1, where R_k is the repunit (A002275) of length k.
5
41, 4441, 44444444441, 4444444444444444444444444441, 4444444444444444444444444444444444444444444444444444441, 4444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444441
OFFSET
1,1
COMMENTS
Primes of the form (4*10^k - 31)/9. - Vincenzo Librandi, Nov 16 2010
CROSSREFS
Cf. A056681 (corresponding k), A173768.
Sequence in context: A282054 A107690 A068815 * A280677 A209104 A233079
KEYWORD
nonn
AUTHOR
Rick L. Shepherd, Mar 27 2004
EXTENSIONS
Edited by N. J. A. Sloane, Feb 26 2010
STATUS
approved