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 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 Alois P. Heinz, Table of n, a(n) for n = 0..1431 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 Cf. A000010, A008683, A340995. Sequence in context: A149803 A259204 A149804 * A301702 A296162 A144036 Adjacent sequences: A340991 A340992 A340993 * A340995 A340996 A340997 KEYWORD nonn AUTHOR Alois P. Heinz, Feb 01 2021 STATUS approved

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