A286108 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).
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
Offset: 0
Examples
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
Links
- Antti Karttunen, Table of n, a(n) for n = 0..10584; the first 145 antidiagonals of array
- Eric Weisstein's World of Mathematics, Pairing Function
Crossrefs
Programs
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Mathematica
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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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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Scheme
(define (A286108 n) (A286108bi (A002262 n) (A025581 n))) (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).
Comments