A214231 Sum of the four nearest neighbors of n in a right triangular type-1 spiral with positive integers.

19, 35, 33, 52, 32, 33, 58, 41, 45, 58, 98, 75, 70, 74, 90, 127, 89, 81, 85, 89, 93, 136, 101, 105, 109, 113, 117, 139, 197, 156, 142, 146, 150, 154, 158, 183, 238, 182, 165, 169, 173, 177, 181, 185, 189, 250, 197, 201, 205, 209, 213, 217, 221, 225, 256, 332

Offset: 1

Author

Alex Ratushnyak, Jul 08 2012

Keywords

• nonn
• easy

Comments

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

Right triangular type-1 spiral implements the sequence Up, Right-down, Left.

Examples

			Right triangular spiral begins:
56
55  57
54  29  58
53  28  30  59
52  27  11  31  60
51  26  10  12  32  61
50  25   9   2  13  33  62
49  24   8   1   3  14  34  63
48  23   7   6   5   4  15  35  64
47  22  21  20  19  18  17  16  36  65
46  45  44  43  42  41  40  39  38  37  66
78  77  76  75  74  73  72  71  70  69  68  67
The four nearest neighbors of 3 are 1, 13, 14, 5. Their sum is a(3)=33.
		

Crossrefs

Cf. A214230 - sum of the 8 nearest neighbors, Python program.

Cf. A214227.