login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A340994 a(n) is the (2n)-th term of the n-fold self-convolution of the Euler totient function phi. 2
1, 1, 5, 19, 89, 391, 1817, 8429, 39697, 187849, 894965, 4282191, 20572961, 99158645, 479294877, 2322365959, 11276837761, 54860498415, 267336028565, 1304677123305, 6375749480369, 31195075605755, 152798541606529, 749184538847397, 3676699991008897 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,3
LINKS
FORMULA
a(n) = [x^(2n)] (Sum_{j>=1} mu(j)*x^j/(1-x^j)^2)^n.
a(n) = A340995(2n,n).
a(n) ~ c * d^n / sqrt(n), where d = 5.0117569538757703168577972551675369123003378927616324330274512382246419... and c = 0.287455327702489527773675891801880332800309441856159133456758815116... - Vaclav Kotesovec, Aug 18 2021
MAPLE
b:= proc(n, k) option remember; `if`(k=0, 1,
`if`(k=1, numtheory[phi](n+1), (q->
add(b(j, q)*b(n-j, k-q), j=0..n))(iquo(k, 2))))
end:
a:= n-> b(n$2):
seq(a(n), n=0..29);
CROSSREFS
Sequence in context: A149803 A259204 A149804 * A301702 A296162 A144036
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Feb 01 2021
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified April 18 03:33 EDT 2024. Contains 371767 sequences. (Running on oeis4.)