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A356343
a(n) = Sum_{k=1..n} binomial(2*n, k) * phi(k), where phi is the Euler totient function.
0
2, 10, 61, 288, 1723, 6524, 37441, 158504, 737019, 2867500, 15200293, 56951428, 291648771, 1141099348, 4686310739, 19016248192, 95307214595, 358297247772, 1748879020425, 6725041736572, 27649247188159, 108460437728204, 522912325647543, 1966622896068784, 8831400010510925
OFFSET
1,1
FORMULA
a(n) ~ 3 * n * 4^n / Pi^2.
MATHEMATICA
Table[Sum[Binomial[2*n, k]*EulerPhi[k], {k, 1, n}], {n, 1, 30}]
PROG
(PARI) a(n) = sum(k=1, n, binomial(2*n, k) * eulerphi(k)); \\ Michel Marcus, Aug 05 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
Vaclav Kotesovec, Aug 04 2022
STATUS
approved