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A153085
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Numbers n such that 4n+5 is not prime
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1
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1, 4, 5, 7, 10, 11, 13, 15, 16, 18, 19, 20, 22, 25, 28, 29, 30, 31, 32, 34, 35, 37, 39, 40, 41, 43, 45, 46, 49, 50, 51, 52, 53, 54, 55, 58, 60, 61, 62, 64, 65, 67, 70, 71, 73, 74, 75, 76, 79, 80, 81, 82, 84, 85, 88, 89, 90, 91
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Let p=2n+1 be an odd number, then A140869(n,n) = (p^2-5)/4 = A028387(n-1).
One less than the associated entry in A045751: a(n)=A045751(n+1)-1. - R. J. Mathar, Jan 05 2011
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EXAMPLE
| 1; *, 5; 4, *, 11; *, 10, *, 19; 7, *, 18, *, 29; *, 15, *, 28, *, 41;
where * mark the entries in A140869 which are non-integer if floor(.) is not applied there.
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CROSSREFS
| Cf. A111215
Sequence in context: A139690 A035266 A035264 * A047259 A039577 A013951
Adjacent sequences: A153082 A153083 A153084 * A153086 A153087 A153088
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KEYWORD
| nonn
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AUTHOR
| Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Dec 18 2008
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