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

Author

Alex Ratushnyak, Dec 04 2012

Keywords

• nonn
• easy

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

Examples

			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.