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Search: id:A121370
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| A121370 |
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Least number k such that (k*M(n))^2 + k*M(n) - 1 is prime with M(i)=i-th Mersenne prime. |
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+0
2
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| 1, 3, 1, 7, 8, 19, 13, 4, 16, 3, 42, 24, 434, 84, 160, 579, 475, 529, 2450, 2644, 5781, 558, 13680, 7146, 1408, 3003, 24455
(list; graph; listen)
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OFFSET
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1,2
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EXAMPLE
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M(4)=2^7-1=127
127^2+127-1=16255 composite
(2*127)^2+2*127-1=64769 composite
(3*127)^2+3*127-1=145541 composite
(4*127)^2+4*127-1=258571 composite
(5*127)^2+5*127-1=403859 composite
(6*127)^2+6*127-1=581405 composite
(7*127)^2+7*127-1=791209 prime so k(4)=7
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CROSSREFS
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Cf. A121371.
Adjacent sequences: A121367 A121368 A121369 this_sequence A121371 A121372 A121373
Sequence in context: A016647 A091039 A120472 this_sequence A137908 A019639 A011207
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KEYWORD
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hard,more,nonn
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AUTHOR
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Pierre CAMI (pierrecami(AT)tele2.fr), Jul 24 2006
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