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Search: id:A096820
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| A096820 |
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Exponents n such that 2^n-21 is prime. |
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+0
4
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| 5, 6, 7, 9, 11, 13, 14, 21, 23, 41, 46, 89, 110, 389, 413, 489, 869, 1589, 1713, 2831, 10843, 11257
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Exponents for primes of 2^n-d form if d=1,3,5,7,11,13,15,17,19,21 found at: A000043 (1); A050414 (3); A059608 (5); A059609 (7); A059610 (9); A096817 (11); A096818 (13); A059612 (15); A059611 (17); A096819 (19); A096820 (21); While at d=1 all exponents are primes, for d=6,19 seems to be all odd, for d=11,17 appears to be even and for others (d=21) no rule I observed.
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EXAMPLE
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n=5: 32-21=11 is prime; n=7: 128-21=107 is prime.
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CROSSREFS
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Cf. A000043(1); A050414(3); A059608(5); A059609(7); A059610(9); A096817(11); A096818(13); A059612(15); A059611(17); A096819(19); A096820(21); A096502[min].
Sequence in context: A066263 A089192 A132829 this_sequence A030388 A031059 A067528
Adjacent sequences: A096817 A096818 A096819 this_sequence A096821 A096822 A096823
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), Jul 13 2004
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