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A107423
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Numbers k equal prime(n)*prime(n+1) such that k+1 is a square and k-1 is even semiprime.
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0
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15, 35, 143, 899, 1763, 5183, 19043, 79523, 213443, 359999, 412163, 685583, 777923, 1192463, 1695203, 2585663, 4536899, 5143823, 5673923, 7225343, 12446783, 12659363, 12830723, 17040383, 17892899, 18818243, 20684303, 25100099
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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EXAMPLE
| a(1)=15 because 3*5=15: 15+1=4^2 and 15-1=2*7;
a(2)=35 because 5*7=35: 35+1=6^2 and 35-1=2*17;
a(3)=143 because 11*13=143: 143+1=12^2 and 143-1=2*71;
a(4)=899 because 29*31=899: 899+1=30^2 and 899-1=2*449;
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CROSSREFS
| Sequence in context: A074480 A194580 A037074 * A027442 A074891 A134509
Adjacent sequences: A107420 A107421 A107422 * A107424 A107425 A107426
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KEYWORD
| nonn
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AUTHOR
| Giovanni Teofilatto (g.teofilatto(AT)tiscalinet.it), May 26 2005
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EXTENSIONS
| Terms beyond a(6) from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jun 28 2010
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