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A374352
a(n) = [n>1] * a(n-1) + Sum_{d|n} phi(lcm(d,n/d)) where [] is an Iverson bracket.
1
1, 3, 7, 12, 20, 28, 40, 52, 66, 82, 102, 122, 146, 170, 202, 228, 260, 288, 324, 364, 412, 452, 496, 544, 588, 636, 684, 744, 800, 864, 924, 980, 1060, 1124, 1220, 1290, 1362, 1434, 1530, 1626, 1706, 1802, 1886, 1986, 2098, 2186, 2278, 2382, 2472, 2560, 2688
OFFSET
1,2
COMMENTS
Sum over all positive integers k, m with k*m <= n of phi(lcm(k,m)).
LINKS
FORMULA
a(n) = Sum_{j=1..n} Sum_{d|j} phi(lcm(d,j/d)).
a(n) = Sum_{j=1..n} A061884(j).
MAPLE
a:= proc(n) option remember; uses numtheory; `if`(n<1, 0,
a(n-1)+add(phi(ilcm(d, n/d)), d=divisors(n)))
end:
seq(a(n), n=1..66);
CROSSREFS
Partial sums of A061884.
Sequence in context: A091369 A036698 A279169 * A132273 A130050 A173256
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Jul 05 2024
STATUS
approved