A030064 1 + product of any two terms is a square.

0, 2, 4, 12, 420

Offset

1,2

References

Martin Gardner, probably "Mathematical Magic Show".

Links

Table of n, a(n) for n=1..5.

A. Baker and H. Davenport, The Equations 3x^2-2=y^2 and 8x^2-7=z^2, Quart. J. Math. Oxford 20 (1969).

Example

0*2,4,12,420 + 1 = 1
2*4 + 1 = 9
2*12 + 1 = 25
2*420 + 1 = 841 -> sqrt = 29
4*12 + 1 = 49
4*420 + 1 = 1681 -> sqrt = 41
12*420 + 1 = 5041 -> sqrt = 71

Crossrefs

Sequence in context: A291827 A287059 A059085 * A224886 A180500 A176990

Adjacent sequences: A030061 A030062 A030063 * A030065 A030066 A030067

Keyword

nonn,fini,full

Author

Timothy Chow (tchow(AT)math.lsa.umich.edu)

Extensions

Corrected by Mitch Harris, Apr 24 2006

Status

approved