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 A320010 Filter sequence combined from those proper divisors of n that are multiples of 3; Restricted growth sequence transform of A319990. 5
 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 (list; graph; refs; listen; history; text; internal format)
 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

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Last modified October 4 00:24 EDT 2023. Contains 365872 sequences. (Running on oeis4.)