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 A289838 a(n) = A289815(n) * A289816(n). 3
 1, 2, 2, 3, 6, 6, 3, 6, 6, 4, 10, 10, 12, 30, 30, 12, 30, 30, 4, 10, 10, 12, 30, 30, 12, 30, 30, 5, 14, 14, 15, 42, 42, 15, 42, 42, 20, 70, 70, 60, 210, 210, 60, 210, 210, 20, 70, 70, 60, 210, 210, 60, 210, 210, 5, 14, 14, 15, 42, 42, 15, 42, 42, 20, 70, 70 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Each number k > 0 appears 2^omega(k) times (where omega = A001221). a(A004488(n)) = a(n) for any n >= 0. The number of distinct prime factors of a(n) equals the number of nonzero digits in the ternary representation of n. LINKS Rémy Sigrist, Table of n, a(n) for n = 0..10000 EXAMPLE a(42) = A289815(42) * A289816(42) = 20 * 3 = 60. PROG (PARI) a(n) = my (v=1);                        \        for (o=2, oo,                           \            if (n==0, return (v));              \            if (gcd(v, o)==1 && omega(o)==1,    \                if (n % 3, v *= o);             \                n \= 3;                         \            );                                  \        ); (Python) from sympy import floor, gcd, primefactors def omega(n): return 0 if n==1 else len(primefactors(n)) def a(n):     v, o = 1, 2     while True:         if n==0: return v         if gcd(v, o)==1 and omega(o)==1:             if n%3: v*=o             n=floor(n/3)         o+=1 print map(a, xrange(101)) # Indranil Ghosh, Aug 02 2017 CROSSREFS Cf. A001221, A004488, A289815, A289816. Sequence in context: A308483 A070871 A096115 * A290734 A093919 A179661 Adjacent sequences:  A289835 A289836 A289837 * A289839 A289840 A289841 KEYWORD nonn,base,look AUTHOR Rémy Sigrist, Jul 13 2017 STATUS approved

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Last modified October 21 20:44 EDT 2019. Contains 328315 sequences. (Running on oeis4.)