A354266 - OEIS

A354266

Pairs of integers (s, t) such that 0 < s < t and gcd(s, t) > 1, where the pairs are generated by the boustrophedonic Cantor enumeration A319571.

2, 4, 2, 6, 3, 6, 2, 8, 4, 6, 2, 10, 3, 9, 4, 8, 2, 12, 4, 10, 6, 8, 3, 12, 5, 10, 6, 9, 2, 14, 4, 12, 6, 10, 2, 16, 3, 15, 4, 14, 6, 12, 8, 10, 2, 18, 4, 16, 5, 15, 6, 14, 8, 12, 3, 18, 6, 15, 7, 14, 9, 12, 2, 20, 4, 18, 6, 16, 8, 14, 10, 12, 2, 22, 3, 21

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OFFSET

1,1

LINKS

Table of n, a(n) for n=1..76.

EXAMPLE

The sequence of pairs starts:

(2, 4), (2, 6), (3, 6), (2, 8), (4, 6), (2, 10), (3, 9), (4, 8), (2, 12), (4, 10),(6, 8), (3, 12), (5, 10), (6, 9), (2, 14), (4, 12), (6, 10), (2, 16), (3, 15),(4, 14), (6, 12), (8, 10), ...

PROG

(Julia)

function A354266List(upto)

L = Int[]

for n in 1:upto

d = div(isqrt(8n + 1) - 1, 2)

s = n - div(d*(d + 1), 2)

t = d - s

if s > 0 && s < t && gcd(s, t) > 1

push!(L, s)

push!(L, t)

end