A320010 - OEIS

A320010

Filter sequence combined from those proper divisors of n that are multiples of 3; Restricted growth sequence transform of A319990.

1, 1, 1, 1, 1, 2, 1, 1, 2, 1, 1, 3, 1, 1, 2, 1, 1, 4, 1, 1, 2, 1, 1, 5, 1, 1, 6, 1, 1, 7, 1, 1, 2, 1, 1, 8, 1, 1, 2, 1, 1, 9, 1, 1, 10, 1, 1, 11, 1, 1, 2, 1, 1, 12, 1, 1, 2, 1, 1, 13, 1, 1, 14, 1, 1, 15, 1, 1, 2, 1, 1, 16, 1, 1, 4, 1, 1, 17, 1, 1, 18, 1, 1, 19, 1, 1, 2, 1, 1, 20, 1, 1, 2, 1, 1, 21, 1, 1, 22, 1, 1, 23, 1, 1, 24

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OFFSET

1,6

COMMENTS

For all i, j: a(i) = a(j) => A320003(i) = A320003(j).

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..65537

PROG

(PARI)

up_to = 65537;

rgs_transform(invec) = { my(om = Map(), outvec = vector(length(invec)), u=1); for(i=1, length(invec), if(mapisdefined(om, invec[i]), my(pp = mapget(om, invec[i])); outvec[i] = outvec[pp] , mapput(om, invec[i], i); outvec[i] = u; u++ )); outvec; };

A019565(n) = {my(j, v); factorback(Mat(vector(if(n, #n=vecextract(binary(n), "-1..1")), j, [prime(j), n[j]])~))}; \\ From A019565

A319990(n) = { my(m=1); fordiv(n, d, if((d<n)&&(0==(d%3)), m *= A019565(d))); m; };

v320010 = rgs_transform(vector(up_to, n, A319990(n)));

A320010(n) = v320010[n];

CROSSREFS

Cf. A319990, A320011, A320012, A320014.

Sequence in context: A153096 A343407 A359236 * A210763 A281681 A218799

Adjacent sequences: A320007 A320008 A320009 * A320011 A320012 A320013

KEYWORD

nonn

AUTHOR

Antti Karttunen, Oct 03 2018

STATUS

approved