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A278545
Number of neighbors of the n-th term in a full square array read by antidiagonals.
3
3, 5, 5, 5, 8, 5, 5, 8, 8, 5, 5, 8, 8, 8, 5, 5, 8, 8, 8, 8, 5, 5, 8, 8, 8, 8, 8, 5, 5, 8, 8, 8, 8, 8, 8, 5, 5, 8, 8, 8, 8, 8, 8, 8, 5, 5, 8, 8, 8, 8, 8, 8, 8, 8, 5, 5, 8, 8, 8, 8, 8, 8, 8, 8, 8, 5, 5, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 5, 5, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 5, 5, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 5
OFFSET
1,1
COMMENTS
Apart from the first row and the first column, the rest of the elements are 8's.
For the same idea but for a right triangle see A278480; for an isosceles triangle see A278481; for a square spiral see A010731; and for a hexagonal spiral see A010722.
LINKS
FORMULA
G.f. 3+x+8*x/(1-x)-3*(1+x)*Theta_2(0,sqrt(x))/(2*x^(1/8)) where Theta_2 is a Jacobi Theta function. - Robert Israel, Dec 04 2016
EXAMPLE
The corner of the square array begins:
3,5,5,5,5,5,5,5,5,5,...
5,8,8,8,8,8,8,8,8,...
5,8,8,8,8,8,8,8,...
5,8,8,8,8,8,8,...
5,8,8,8,8,8,...
5,8,8,8,8,...
5,8,8,8,...
5,8,8,...
5,8,...
5,...
...
MAPLE
3, seq(op([5, 8$i, 5]), i=0..20); # Robert Israel, Dec 04 2016
CROSSREFS
Antidiagonal sums give 3 together with the elements > 2 of A017089.
Sequence in context: A141791 A196158 A290561 * A023828 A120133 A088961
KEYWORD
nonn,tabl
AUTHOR
Omar E. Pol, Nov 23 2016
STATUS
approved