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A286108
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Square array read by antidiagonals: A(n,k) = T(2*(n AND k), n XOR k), where T(n,k) is sequence A001477 considered as a two-dimensional table, AND is bitwise-and (A004198) and XOR is bitwise-xor (A003987).
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7
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0, 1, 1, 3, 5, 3, 6, 6, 6, 6, 10, 12, 14, 12, 10, 15, 15, 19, 19, 15, 15, 21, 23, 21, 27, 21, 23, 21, 28, 28, 28, 28, 28, 28, 28, 28, 36, 38, 40, 38, 44, 38, 40, 38, 36, 45, 45, 49, 49, 53, 53, 49, 49, 45, 45, 55, 57, 55, 61, 63, 65, 63, 61, 55, 57, 55, 66, 66, 66, 66, 74, 74, 74, 74, 66, 66, 66, 66, 78, 80, 82, 80, 78, 88, 90, 88, 78, 80, 82, 80, 78
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OFFSET
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0,4
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COMMENTS
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The array is read by descending antidiagonals as A(0,0), A(0,1), A(1,0), A(0,2), A(1,1), A(2,0), ...
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LINKS
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FORMULA
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A(n,k) = T(2*A004198(n,k), A003987(n,k)), where T(n,k) is sequence A001477 considered as a two-dimensional table, that is, as a pairing function from [0, 1, 2, 3, ...] x [0, 1, 2, 3, ...] to [0, 1, 2, 3, ...].
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EXAMPLE
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The top left 0 .. 12 x 0 .. 12 corner of the array:
0, 1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 66, 78
1, 5, 6, 12, 15, 23, 28, 38, 45, 57, 66, 80, 91
3, 6, 14, 19, 21, 28, 40, 49, 55, 66, 82, 95, 105
6, 12, 19, 27, 28, 38, 49, 61, 66, 80, 95, 111, 120
10, 15, 21, 28, 44, 53, 63, 74, 78, 91, 105, 120, 144
15, 23, 28, 38, 53, 65, 74, 88, 91, 107, 120, 138, 161
21, 28, 40, 49, 63, 74, 90, 103, 105, 120, 140, 157, 179
28, 38, 49, 61, 74, 88, 103, 119, 120, 138, 157, 177, 198
36, 45, 55, 66, 78, 91, 105, 120, 152, 169, 187, 206, 226
45, 57, 66, 80, 91, 107, 120, 138, 169, 189, 206, 228, 247
55, 66, 82, 95, 105, 120, 140, 157, 187, 206, 230, 251, 269
66, 80, 95, 111, 120, 138, 157, 177, 206, 228, 251, 275, 292
78, 91, 105, 120, 144, 161, 179, 198, 226, 247, 269, 292, 324
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MATHEMATICA
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T[a_, b_]:=((a + b)^2 + 3a + b)/2; A[n_, k_]:=T[2*BitAnd[n, k], BitXor[n, k]]; Table[A[k, n - k ], {n, 0, 20}, {k, 0, n}] // Flatten (* Indranil Ghosh, May 20 2017 *)
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PROG
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(Scheme)
(define (A286108bi row col) (let ((a (* 2 (A004198bi row col))) (b (A003987bi row col))) (/ (+ (expt (+ a b) 2) (* 3 a) b) 2))) ;; Here A003987bi and A004198bi implement bitwise-xor (A003987) and bitwise-and (A004198).
(Python)
def T(a, b): return ((a + b)**2 + 3*a + b)//2
def A(n, k): return T(2*(n&k), n^k)
for n in range(21): print([A(k, n - k) for k in range(n + 1)]) # Indranil Ghosh, May 20 2017
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CROSSREFS
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KEYWORD
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AUTHOR
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STATUS
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approved
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