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 A073254 Table of n^2 + n*k + k^2 by antidiagonals. 7
 0, 1, 1, 4, 3, 4, 9, 7, 7, 9, 16, 13, 12, 13, 16, 25, 21, 19, 19, 21, 25, 36, 31, 28, 27, 28, 31, 36, 49, 43, 39, 37, 37, 39, 43, 49, 64, 57, 52, 49, 48, 49, 52, 57, 64, 81, 73, 67, 63, 61, 61, 63, 67, 73, 81, 100, 91, 84, 79, 76, 75, 76, 79, 84, 91, 100, 121, 111, 103, 97 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 COMMENTS Norm of elements in planar hexagonal lattice A_2. LINKS FORMULA T(n,k) = k^2-kn+n^2. T(n,k) = Sum{j=0..m} Sum{i=0..m} (-1)^(j+i)*C(i,j)*n^j*k^(m-j) for m = 2. T(n,0) = T(n,n) = n^m = n^2 = A000290(n). T(2n,n) = (m+1)n^m = 3n^2 = A033428(n). T(2n+1,n+1) = (n+1)^(m+1)-n^(m+1) = (n+1)^3-n^3 = A003215(n). Sum{k=0..n} T(n,k) = (5n^3+6n^2+n)/6 = A033994(n). T(n+1,k+1)C(n,k)^3/(k+1)^2 = A194595(n,k). - Peter Luschny, Oct 26 2011 EXAMPLE [0]               0 [1]              1, 1 [2]            4, 3, 4 [3]           9, 7, 7, 9 [4]       16, 13, 12, 13, 16 [5]     25, 21, 19, 19, 21, 25 [6]   36, 31, 28, 27, 28, 31, 36 [7] 49, 43, 39, 37, 37, 39, 43, 49 MAPLE A073254 := (n, k) -> k^2-k*n+n^2: # Peter Luschny, Oct 26 2011 MATHEMATICA T[n_, k_] := n^2 + n k + k^2; Table[T[n-k, k], {n, 0, 11}, {k, 0, n}] // Flatten (* Jean-François Alcover, Jun 22 2018 *) PROG (PARI) {T(n, k) = n^2 + n*k + k^2} CROSSREFS A033994 gives antidiagonal sums. Cf. A004016, A057427, A003056, A198063, A198064, A198065. Sequence in context: A132984 A277528 A118701 * A094177 A249453 A244954 Adjacent sequences:  A073251 A073252 A073253 * A073255 A073256 A073257 KEYWORD nonn,tabl,easy AUTHOR Michael Somos, Jul 23 2002 STATUS approved

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Last modified January 19 14:53 EST 2020. Contains 331049 sequences. (Running on oeis4.)