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A140109 Quartets of prime x, composites y, z and S for Heron's formula. 0
7, 15, 20, 42, 7, 24, 25, 84, 13, 14, 15, 84, 13, 84, 85, 546, 17, 8, 15, 60, 17, 9, 10, 36, 29, 20, 21, 210, 37, 12, 35, 210, 41, 9, 40, 180, 53, 45, 48, 1080, 73, 48, 55, 1320, 89, 39, 80, 1560, 97, 65, 72, 2340, 101, 20, 99, 990, 109, 60, 91, 2730, 113, 15, 112, 840 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Heron's formula (x+y+z)*(x+y-z)*(x+z-y)*(y+z-x)/16=S^2

LINKS

Table of n, a(n) for n=1..64.

EXAMPLE

The quartets are: (7, 15, 20, 42), (7, 24, 25, 84), (13, 14, 15, 84), etc.

CROSSREFS

Cf. A140385, A140391, A140384.

Sequence in context: A297853 A298050 A115783 * A064397 A214467 A151971

Adjacent sequences:  A140106 A140107 A140108 * A140110 A140111 A140112

KEYWORD

nonn

AUTHOR

Juri-Stepan Gerasimov, Jul 10 2008

EXTENSIONS

This should be replaced by four linked sequences! As it stands it is not a proper sequence. - N. J. A. Sloane, Jul 11 2008

STATUS

approved

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Last modified October 22 17:39 EDT 2019. Contains 328319 sequences. (Running on oeis4.)