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A238374
Row sums of triangle in A204026.
0
1, 2, 4, 6, 9, 12, 17, 22, 30, 38, 51, 64, 85, 106, 140, 174, 229, 284, 373, 462, 606, 750, 983, 1216, 1593, 1970, 2580, 3190, 4177, 5164, 6761, 8358, 10942, 13526, 17707, 21888, 28653, 35418, 46364, 57310, 75021, 92732, 121389, 150046, 196414, 242782
OFFSET
0,2
FORMULA
G.f.: (1+x)*(1+x^2)/((1-x^2-x^4)*(1-x)).
a(n) = a(n-1) + a(n-2) - a(n-3) + a(n-4) - a(n-5), a(0) = 1, a(1) = 2, a(2) = 4, a(3) = 6, a(4) = 9.
a(2*n) = A157728(n+5) = A000045(n+5) - 4.
a(2*n+1) = 2*A001911(n+1) = 2*A000045(n+4) - 4.
EXAMPLE
Triangle in A204026 begins:
1;.........................sum = 1
1, 1;......................sum = 2
1, 2, 1;...................sum = 4
1, 2, 2, 1;................sum = 6
1, 2, 3, 2, 1;.............sum = 9
1, 2, 3, 3, 2, 1;..........sum = 12
1, 2, 3, 5, 3, 2, 1;.......sum = 17
1, 2, 3, 5, 5, 3, 2, 1;....sum = 22
1, 2, 3, 5, 8, 5, 3, 2, 1;.sum = 30
MATHEMATICA
LinearRecurrence[{1, 1, -1, 1, -1}, {1, 2, 4, 6, 9}, 50] (* Harvey P. Dale, Feb 24 2018 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Philippe Deléham, Feb 25 2014
STATUS
approved