[seqfan] two dumb questions
Peter Lawrence
peterl95124 at sbcglobal.net
Sat Jul 22 03:43:47 CEST 2017
A051731: characteristic triangle of divisors of n
A000005: = number of divisors of n = row sums of A051731
1. How is A051731 different from Redheffer matrix A143104,
which seems to have same FORMULA definition ?
a(i,j) = 1 if j=1 or j|i; 0 otherwise.
Axxxxxx: characteristic triangle of numbers with gcd( I, j ) = 1
A000010 = number of relative-primes of n = row sums of Axxxxxx
a(i,j) = 1 if gcd(j,i) = 1; 0 otherwise.
1: 1, 1
2: 1, 0, 1
3: 1, 1, 0, 2
4: 1, 0, 1, 0, 2
5: 1, 1, 1, 1, 0, 4
6: 1, 0, 0, 1, 0, 0, 2
7: 1, 1, 1, 1, 1, 1, 0, 6
8: 1, 0, 1, 0, 1, 0, 1, 0, 4
9: 1, 1, 0, 1, 1, 0, 1, 1, 0, 6
10: 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 4
11: 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 10
12: 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 4
13: 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 12
14: 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 6
15: 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 8
16: 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 8
2. I suspect I computed this triangle incorrectly, because I can’t find it in the OEIS _?_
Peter Lawrence.
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