

A231425


The Schramm triangle: T(n,k) = f(gcd(n,k)), where f = Dirichlet inverse of Euler totient.


2



1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 4, 1, 1, 2, 1, 1, 2, 1, 1, 1, 1, 1, 1, 6, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 2, 1, 1, 2, 1, 1, 1, 1, 4, 1, 1, 1, 1, 4, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 10, 1, 1, 2, 1, 1, 2, 1, 1, 2, 1, 1, 2
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OFFSET

1,6


COMMENTS

When taking matrix powers of the reversed triangle it might be more interesting to start with the first term T(1,1) set to 0.
Three fundamental number theoretic sequences are found from this triangle. The first is the Dirichlet inverse of the Euler totient which are the entries themselves. The Greatest Common DivisorFourier transform described by Wolfgang Schramm gives the Möbius function times n =1, 2, 3, 0, ... = A055615, as follows:
1*cos(2*k*Pi/n) = 1
1*cos(2*k*Pi/n) 1*cos(2*k*Pi/n) = 2
1*cos(2*k*Pi/n) +1*cos(2*k*Pi/n) 2*cos(2*k*Pi/n) = 3
The two components in this GCDFourier triangle both sum to the sequence 1,0,0,0,0, ... A000007.
1 = 1
1 1 = 0
1 +1 2 = 0
...
cos(2*k*Pi/n) = 1
cos(2*k*Pi/n), cos(2*k*Pi/n) = 0
cos(2*k*Pi/n), cos(2*k*Pi/n), cos(2*k*Pi/n) = 0
...
This latter Fourier transform like triangle is also called the chaotic set by some authors.
The third arithmetic sequence is the von Mangoldt function that can be computed as sums with periods equal to rows in this triangle:
1
log(2) = Sum_{n>=0} (1/(n+1) 1/(n+2))
log(3) = Sum_{n>=0} (1/(n+1) +1/(n+2) 2/(n+3))
log(2) = Sum_{n>=0} (1/(n+1) 1/(n+2) +1/(n+3) 1/(n+4))
log(5) = Sum_{n>=0} (1/(n+1) +1/(n+2) +1/(n+3) +1/(n+4) 4/(n+5))
log(1) = Sum_{n>=0} (1/(n+1) 1/(n+2) 2/(n+3) 1/(n+4) +1/(n+5) +2/(n+6))
...
Also the matrix inverse of the reversal of this number triangle gives the allones sequence in the first column. Therefore this number triangle is a companion to A054524.
A subset and also a companion to this triangle in terms of Greatest Common Divisor Fourier transform is A054521, since from A054521 one gets the Mobius function while from this triangle one gets the Möbius function elementwise multiplied by the natural numbers.
The special polynomial found in A199514 is also the solution to the rowwise equations of the symmetric polynomial described in A199514 times the chaotic set or Greatest Common Divisor Fourier transform, so that A199514 is the solution.


LINKS



FORMULA

T(n,k) = A023900(gcd(n,k)) for n >= k.


MATHEMATICA

Clear[nn, t, n, k]; nn = 12; t[n_, 1] = 1; t[1, k_] = 1;
t[n_, k_] := t[n, k] = If[n >= k, Sum[t[n  i, k], {i, 1, k  1}], Sum[t[k  i, n], {i, 1, n  1}]]; Flatten[Table[Table[t[n, k], {k, 1, n}], {n, 1, nn}]]


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STATUS

approved



