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A094728
Triangle read by rows: T(n,k) = n^2 - k^2, 0 <= k < n.
15
1, 4, 3, 9, 8, 5, 16, 15, 12, 7, 25, 24, 21, 16, 9, 36, 35, 32, 27, 20, 11, 49, 48, 45, 40, 33, 24, 13, 64, 63, 60, 55, 48, 39, 28, 15, 81, 80, 77, 72, 65, 56, 45, 32, 17, 100, 99, 96, 91, 84, 75, 64, 51, 36, 19, 121, 120, 117, 112, 105, 96, 85, 72, 57, 40, 21
OFFSET
1,2
COMMENTS
(T(n,k) mod 4) <> 2, see A042965, A016825.
All numbers m occur A034178(m) times.
The row polynomials T(n,x) appear in the calculation of the column g.f.s of triangle A120070 (used to find the frequencies of the spectral lines of the hydrogen atom).
LINKS
FORMULA
Row polynomials: T(n,x) = n^2*Sum_{m=0..n} x^m - Sum_{m=0..n} m^2*x^m = Sum_{k=0..n-1} T(n,k)*x^k, n >= 1.
T(n, k) = A004736(n,k)*A094727(n,k).
T(n, 0) = A000290(n).
T(n, 1) = A005563(n-1) for n>1.
T(n, 2) = A028347(n) for n>2.
T(n, 3) = A028560(n-3) for n>3.
T(n, 4) = A028566(n-4) for n>4.
T(n, n-1) = A005408(n).
T(n, n-2) = A008586(n-1) for n>1.
T(n, n-3) = A016945(n-2) for n>2.
T(n, n-4) = A008590(n-2) for n>3.
T(n, n-5) = A017329(n-3) for n>4.
T(n, n-6) = A008594(n-3) for n>5.
T(n, n-8) = A008598(n-2) for n>7.
T(A005408(k), k) = A000567(k).
Sum_{k=0..n} T(n, k) = A002412(n) (row sums).
From G. C. Greubel, Mar 12 2024: (Start)
Sum_{k=0..n-1} (-1)^k * T(n, k) = A000384(floor((n+1)/2)).
Sum_{k=0..floor((n-1)/2)} T(n-k, k) = A128624(n).
Sum_{k=0..floor((n-1)/2)} (-1)^k*T(n-k, k) = (1/2)*n*(n+1 - (-1)^n*cos(n*Pi/2)). (End)
EXAMPLE
n=3: T(3,x) = 9+8*x+5*x^2.
Triangle begins:
1;
4, 3;
9, 8, 5;
16, 15, 12, 7;
25, 24, 21, 16, 9;
36, 35, 32, 27, 20, 11;
49, 48, 45, 40, 33, 24, 13;
64, 63, 60, 55, 48, 39, 28, 15;
81, 80, 77, 72, 65, 56, 45, 32, 17;
... etc. - Philippe Deléham, Mar 07 2013
MATHEMATICA
Table[n^2 - k^2, {n, 12}, {k, 0, n-1}]//Flatten (* Michael De Vlieger, Nov 25 2015 *)
PROG
(Magma) [n^2-k^2: k in [0..n-1], n in [1..15]]; // G. C. Greubel, Mar 12 2024
(SageMath) flatten([[n^2-k^2 for k in range(n)] for n in range(1, 16)]) # G. C. Greubel, Mar 12 2024
CROSSREFS
KEYWORD
nonn,tabl,easy
AUTHOR
Reinhard Zumkeller, May 24 2004
STATUS
approved