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A022267 n*(9n+1)/2. +0
2
0, 5, 19, 42, 74, 115, 165, 224, 292, 369, 455, 550, 654, 767, 889, 1020, 1160, 1309, 1467, 1634, 1810, 1995, 2189, 2392, 2604, 2825, 3055, 3294, 3542, 3799, 4065, 4340, 4624, 4917, 5219, 5530, 5850, 6179 (list; graph; listen)
OFFSET

0,2

COMMENT

Write 0,1,2,3,4,... in a triangular spiral, then a(n) is the sequence found by reading the line from 0 in the direction 0,5,... - Floor van Lamoen (fvlamoen(AT)hotmail.com), Jul 21 2001. The spiral begins:

..........15

........16..14

......17..3...13

....18..4...2...12

..19..5...0...1...11

20..6...7...8...9...10

LINKS

Milan Janjic, Two Enumerative Functions

MAPLE

seq(binomial(9*n+1, 2)/9, n=0..37); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jan 21 2007

CROSSREFS

Cf. A051682.

a(n) = A110449(n,4) for n>3.

Sequence in context: A091568 A089148 A098319 this_sequence A094465 A020580 A045458

Adjacent sequences: A022264 A022265 A022266 this_sequence A022268 A022269 A022270

KEYWORD

nonn

AUTHOR

njas

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Last modified July 8 18:40 EDT 2008. Contains 141013 sequences.


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