A318887 - OEIS

A318887

Filter sequence related to the differences of prime factors of n.

1, 2, 2, 3, 2, 4, 2, 5, 3, 6, 2, 7, 2, 8, 9, 10, 2, 11, 2, 12, 13, 14, 2, 15, 3, 16, 5, 17, 2, 18, 2, 19, 20, 21, 9, 22, 2, 23, 24, 25, 2, 26, 2, 27, 28, 29, 2, 30, 3, 31, 32, 33, 2, 34, 35, 36, 37, 38, 2, 39, 2, 40, 41, 42, 20, 43, 2, 44, 45, 46, 2, 47, 2, 48, 49, 50, 13, 51, 2, 52, 10, 53, 2, 54, 55, 56, 57, 58, 2, 59, 35, 60, 61, 62, 32, 63, 2, 64, 65, 66, 2

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

COMMENTS

Restricted growth sequence transform of A318885.

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..100000

PROG

(PARI)

up_to = 100000;

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; };

A318885(n) = if(1==n, n, my(f=factor(n), m=2^f[1, 2], i=1); for(k=2, #f~, i += (f[k, 1]-f[k-1, 1]); m *= prime(i)^f[k, 2]); (m));

v318887 = rgs_transform(vector(up_to, n, A318885(n)));

A318887(n) = v318887[n];

CROSSREFS

Cf. A318885, A318888.

Sequence in context: A355834 A300248 A300247 * A305975 A304751 A117658

Adjacent sequences: A318884 A318885 A318886 * A318888 A318889 A318890

KEYWORD

nonn

AUTHOR

Antti Karttunen, Sep 24 2018

STATUS

approved