A214227 - OEIS

A214227

Sum of the four nearest neighbors of n in a triangular spiral with positive integers.

%I #14 Aug 25 2018 02:44:38

%S 24,32,20,28,56,44,64,48,60,88,60,56,60,64,68,84,128,100,92,96,136,

%T 104,108,112,132,176,132,120,124,128,132,136,140,144,148,172,232,188,

%U 172,176,180,184,240,192,196,200,204,208,236,296,236,216,220,224,228,232,236

%N Sum of the four nearest neighbors of n in a triangular spiral with positive integers.

%C Nearby numbers on diagonals are not counted as neighbors for this sequence.

%C The central 1 is at ?

%e Triangular spiral begins:

%e .

%e 43

%e / \

%e 42 21 44

%e / / \ \

%e 41 20 7 22 45

%e / / / \ \ \

%e 40 19 6 1 8 23 46

%e / / / \ \ \ \

%e 39 18 5--4--3--2 9 24 47

%e / / \ \ \

%e 38 17-16-15-14-13-12-11-10 25 48

%e / \ \

%e 37-36-35-34-33-32-31-30-29-28-27-26 49

%e \

%e 64-63-62-61-60-59-58-57-56-55-54-53-52-51-50

%e .

%e The four nearest neighbors of 3 are 1, 4, 2, 13; their sum is a(3)=20.

%Y Cf. A214226 (sum of the 8 nearest neighbors).

%K nonn,easy

%O 1,1

%A _Alex Ratushnyak_, Jul 07 2012