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A308445
a(0) = 1; a(n) = Sum_{k=1..n} gcd(n,k)*a(n-k).
0
1, 1, 3, 7, 18, 34, 104, 174, 510, 1082, 2714, 4658, 16316, 25634, 71978, 169258, 419878, 712386, 2349160, 3773934, 11980874, 25033510, 59450390, 104012646, 368769280, 625406094, 1645569502, 3654549058, 9504389550, 16006708782, 55050007424, 87063424990
OFFSET
0,3
MATHEMATICA
a[n_] := a[n] = Sum[GCD[n, k] a[n - k], {k, 1, n}]; a[0] = 1; Table[a[n], {n, 0, 31}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, May 27 2019
STATUS
approved