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A333121
a(1) = 1; a(n+1) = Product_{d|n} (1 + a(d)).
0
1, 2, 6, 14, 90, 182, 7686, 15374, 1383750, 19372514, 10577393190, 21154786382, 2438935322096070, 4877870644192142, 224977149851430019446, 286620888910721844775478, 396611655030211352708069066250, 793223310060422705416138132502, 8436334593920261958919014477018674175558
OFFSET
1,2
MATHEMATICA
a[1] = 1; a[n_] := a[n] = Product[1 + a[d], {d, Divisors[n - 1]}]; Table[a[n], {n, 1, 19}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Mar 08 2020
STATUS
approved