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

1,1

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.

Links

Table of n, a(n) for n=1..56.

Example

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.

Sequence in context: A235869 A140601 A031206 * A242847 A044064 A044445

Adjacent sequences: A214228 A214229 A214230 * A214232 A214233 A214234

Keyword

nonn,easy

Author

Alex Ratushnyak, Jul 08 2012

Status

approved