OFFSET
1,1
COMMENTS
Nearby numbers on diagonals are not counted as neighbors for this sequence.
The central 1 is at ?
EXAMPLE
Triangular spiral begins:
.
43
/ \
/ \
42 21 44
/ / \ \
/ / \ \
41 20 7 22 45
/ / / \ \ \
/ / / \ \ \
40 19 6 1 8 23 46
/ / / \ \ \ \
/ / / \ \ \ \
39 18 5--4--3--2 9 24 47
/ / \ \ \
/ / \ \ \
38 17-16-15-14-13-12-11-10 25 48
/ \ \
/ \ \
37-36-35-34-33-32-31-30-29-28-27-26 49
\
\
64-63-62-61-60-59-58-57-56-55-54-53-52-51-50
.
The four nearest neighbors of 3 are 1, 4, 2, 13; their sum is a(3)=20.
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Alex Ratushnyak, Jul 07 2012
STATUS
approved