A293221 a(n) = Product_{d|n, d<n} A019565(A289813(d)); a product obtained from the 1-digits present in ternary expansions of proper divisors of n.

1, 2, 2, 2, 2, 6, 2, 12, 6, 6, 2, 36, 2, 4, 18, 12, 2, 30, 2, 360, 12, 10, 2, 540, 6, 60, 30, 360, 2, 900, 2, 120, 30, 10, 12, 2700, 2, 4, 180, 360, 2, 540, 2, 360, 450, 6, 2, 5400, 4, 120, 30, 360, 2, 210, 30, 5040, 12, 14, 2, 1701000, 2, 84, 180, 2520, 180, 1260, 2, 840, 18, 12600, 2, 94500, 2, 140, 180, 840, 20, 18900, 2, 756000, 210, 210, 2, 23814000, 30

Offset

1,2

Links

Antti Karttunen, Table of n, a(n) for n = 1..6561

Formula

a(n) = Product_{d|n, d<n} A019565(A289813(d)).

For all n >= 0, a(3^n) = A002110(n).

Prog

(PARI)
A019565(n) = {my(j, v); factorback(Mat(vector(if(n, #n=vecextract(binary(n), "-1..1")), j, [prime(j), n[j]])~))}; \\ This function from M. F. Hasler
A289813(n) = { my (d=digits(n, 3)); fromdigits(vector(#d, i, if (d[i]==1, 1, 0)), 2); } \\ From _Remy Sigrist_
A293221(n) = { my(m=1); fordiv(n, d, if(d < n, m *= A019565(A289813(d)))); m; };

Crossrefs

Cf. A019565, A289813, A293214, A293222, A293223 (restricted growth sequence transform), A293226.

Cf. also A290091.

Sequence in context: A351031 A328236 A119462 * A334512 A096625 A359072

Adjacent sequences: A293218 A293219 A293220 * A293222 A293223 A293224

Keyword

nonn,base

Author

Antti Karttunen, Oct 03 2017

Status

approved