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A226455 G.f.: exp( Sum_{n>=1} A056789(n)*x^n/n ), where A056789(n) = Sum_{k=1..n} lcm(k,n)/gcd(k,n). 0
1, 1, 2, 5, 10, 23, 40, 86, 159, 300, 559, 1037, 1887, 3400, 6102, 10763, 19027, 33138, 57621, 99160, 169934, 289432, 490208, 826169, 1385272, 2312155, 3840729, 6354981, 10467872, 17179510, 28081845, 45740041, 74234336, 120074489, 193582842, 311102311, 498434393 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..36.

FORMULA

G.f.: (1/(1 - x)) * Product_{k>=2} 1/(1 - x^k)^(phi(k^2)/2), where phi() is the Euler totient function. - Ilya Gutkovskiy, May 28 2019

EXAMPLE

G.f.: A(x) = 1 + x + 2*x^2 + 5*x^3 + 10*x^4 + 23*x^5 + 40*x^6 + 86*x^7 + ...

where

log(A(x)) = x + 3*x^2/2 + 10*x^3/3 + 19*x^4/4 + 51*x^5/5 + 48*x^6/6 + 148*x^7/7 + 147*x^8/8 + 253*x^9/9 + 253*x^10/10 + ... + A056789(n)*x^n/n + ...

PROG

(PARI) {A056789(n)=sum(k=1, n, lcm(n, k)/gcd(n, k))}

{a(n)=polcoeff(exp(sum(m=1, n+1, A056789(m)*x^m/m)+x*O(x^n)), n)}

for(n=0, 30, print1(a(n), ", "))

CROSSREFS

Cf. A056789.

Sequence in context: A015902 A301427 A300275 * A284139 A068054 A174542

Adjacent sequences:  A226452 A226453 A226454 * A226456 A226457 A226458

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Jun 07 2013

STATUS

approved

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Last modified June 19 12:45 EDT 2021. Contains 345129 sequences. (Running on oeis4.)