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A153275
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Numbers n such that 10*n+1 is not prime.
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0
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0, 2, 5, 8, 9, 11, 12, 14, 16, 17, 20, 22, 23, 26, 29, 30, 32, 34, 35, 36, 37, 38, 39, 41, 44, 45, 47, 48, 50, 51, 53, 55, 56, 58, 59, 61, 62, 65, 67, 68, 71, 72, 73, 74, 77, 78, 79, 80, 83, 84, 85, 86, 87, 89, 90, 92, 93, 95, 96, 98, 100, 101, 104, 107, 108, 110
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Multiplied by 2 we have 4,10,16,18,... which is the set of even terms of A153329. [From R. J. Mathar, Jan 23 2009]
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FORMULA
| Let p = prime number, n=(p^2-1)/10 mod (p); or, n=(p^2+4p-1)/10 mod (p); or, n=(p^2+6p-1)/10 mod (p)
a(n) = (A053178(n)-1)/10. [From R. J. Mathar, Oct 30 2009]
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CROSSREFS
| Cf. A024912.
Sequence in context: A068537 A047620 A062803 * A161154 A174438 A176061
Adjacent sequences: A153272 A153273 A153274 * A153276 A153277 A153278
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KEYWORD
| nonn
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AUTHOR
| Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Dec 22 2008
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EXTENSIONS
| 63 replaced by 53. - R. J. Mathar, Jan 23 2009
0 added by Arkadiusz Wesolowski, Aug 03 2011
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