OFFSET
0,3
COMMENTS
To evaluate a(n) consider only the two largest neighbors of a(n) that are present in the spiral when a(n) should be a new term in the spiral.
It appears that the same idea for an isosceles triangle and also for a square array gives A030237.
EXAMPLE
Illustration of initial terms as a spiral:
.
. 18 - 15 - 12
. / \
. 22 3 - 2 10
. / / \ \
. 26 4 1 - 1 8
. \ \ /
. 31 5 - 6 - 7
. \
. 36 - 42 - 49
.
a(16) = 36 because the sum of its two largest neighbors is 31 + 5 = 36.
a(17) = 42 because the sum of its two largest neighbors is 36 + 6 = 42.
a(18) = 49 because the sum of its two largest neighbors is 42 + 7 = 49.
a(19) = 56 because the sum of its two largest neighbors is 49 + 7 = 56.
CROSSREFS
KEYWORD
nonn
AUTHOR
Omar E. Pol, Nov 24 2016
STATUS
approved