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A077064
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Squarefree numbers of form prime - 1.
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6
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1, 2, 6, 10, 22, 30, 42, 46, 58, 66, 70, 78, 82, 102, 106, 130, 138, 166, 178, 190, 210, 222, 226, 238, 262, 282, 310, 330, 346, 358, 366, 382, 418, 430, 438, 442, 462, 466, 478, 498, 502, 546, 562, 570, 586, 598, 606, 618, 642, 646, 658, 682, 690, 718, 742
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OFFSET
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1,2
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COMMENTS
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This sequence is infinite and its relative density in the sequence of primes is equal to Artin's constant (A005596): Product_{p prime} (1-1/(p*(p-1)) = 0.373955... (Victorovich, 2013). - Amiram Eldar, Dec 29 2020
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LINKS
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EXAMPLE
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MATHEMATICA
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Select[Prime[Range[200]]-1, SquareFreeQ] (* Harvey P. Dale, Feb 09 2015 *)
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PROG
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(PARI) isok(n) = issquarefree(n) && isprime(n+1); \\ Michel Marcus, Mar 22 2016
(PARI) lista(nn) = forprime(p=2, nn, if (issquarefree(p-1), print1(p-1, ", "))); \\ Michel Marcus, Mar 22 2016
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CROSSREFS
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KEYWORD
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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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