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A107423 Numbers k equal prime(n)*prime(n+1) such that k+1 is a square and k-1 is even semiprime. 0
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; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..28.

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;

CROSSREFS

Sequence in context: A194580 A210503 A037074 * A027442 A208728 A219689

Adjacent sequences:  A107420 A107421 A107422 * A107424 A107425 A107426

KEYWORD

nonn

AUTHOR

Giovanni Teofilatto, May 26 2005

EXTENSIONS

Terms beyond a(6) from R. J. Mathar, Jun 28 2010

STATUS

approved

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Last modified April 18 10:38 EDT 2019. Contains 322209 sequences. (Running on oeis4.)