OFFSET
1,1
FORMULA
From Ilya Gutkovskiy, Mar 22 2020: (Start)
a(n) = Sum_{d|n} A023900(n/d) * prime(d).
Sum_{k=1..n} a(gcd(n,k)) = prime(n). (End)
EXAMPLE
a(4) = 2 = dot product of row 4 of A129691: (-1, -1, 0, 1) and the first four primes: (2, 3, 5, 7) = (-2, -3, 0, 7) = 2.
CROSSREFS
KEYWORD
sign
AUTHOR
Gary W. Adamson, May 02 2007
EXTENSIONS
New name and more terms from Ilya Gutkovskiy, Mar 22 2020
STATUS
approved