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A214227
Sum of the four nearest neighbors of n in a triangular spiral with positive integers.
3
24, 32, 20, 28, 56, 44, 64, 48, 60, 88, 60, 56, 60, 64, 68, 84, 128, 100, 92, 96, 136, 104, 108, 112, 132, 176, 132, 120, 124, 128, 132, 136, 140, 144, 148, 172, 232, 188, 172, 176, 180, 184, 240, 192, 196, 200, 204, 208, 236, 296, 236, 216, 220, 224, 228, 232, 236
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
Cf. A214226 (sum of the 8 nearest neighbors).
Sequence in context: A206448 A266984 A217158 * A337055 A064673 A034782
KEYWORD
nonn,easy
AUTHOR
Alex Ratushnyak, Jul 07 2012
STATUS
approved