A220100 Sum of the four nearest neighbors of n in a double spiral with positive integers and 1 at the center.

18, 27, 26, 42, 42, 34, 35, 42, 42, 74, 74, 58, 58, 66, 66, 106, 106, 82, 82, 90, 90, 98, 98, 106, 106, 154, 154, 122, 122, 130, 130, 138, 138, 146, 146, 202, 202, 162, 162, 170, 170, 178, 178, 186, 186, 194, 194, 202, 202, 266, 266, 218, 218, 226, 226, 234, 234, 242

Offset

1,1

Comments

Double spiral begins:

.

82---84---86---88---90---92---94---96---98

|

80 51---53---55---57---59---61---63---65

| | |

78 49 26---28---30---32---34---36 67

| | | | |

76 47 24 11---13---15---17 38 69

| | | | | | |

74 45 22 9 2----4 19 40 71

| | | | | | | | |

72 43 20 7 1 6 21 42 73

| | | | | | | | |

70 41 18 5----3 8 23 44 75

| | | | | | |

68 39 16---14---12---10 25 46 77

| | | | |

66 37---35---33---31---29---27 48 79

| | |

64---62---60---58---56---54---52---50 81

|

99---97---95---93---91---89---87---85---83

Links

Table of n, a(n) for n=1..58.

Example

The four nearest neighbors of 8 are 3, 6, 23, 10; their sum is a(8)=42.
The four nearest neighbors of 9 are 22, 11, 2, 7; their sum is a(9)=42.

Crossrefs

Cf. A220098, A220099.

Sequence in context: A003634 A338383 A338385 * A080910 A390509 A347826

Adjacent sequences: A220097 A220098 A220099 * A220101 A220102 A220103

Keyword

nonn,easy

Author

Alex Ratushnyak, Dec 04 2012

Status

approved