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A305973 Filter sequence for the prime signature of 2n-1. 7
1, 2, 2, 2, 3, 2, 2, 4, 2, 2, 4, 2, 3, 5, 2, 2, 4, 4, 2, 4, 2, 2, 6, 2, 3, 4, 2, 4, 4, 2, 2, 6, 4, 2, 4, 2, 2, 6, 4, 2, 7, 2, 4, 4, 2, 4, 4, 4, 2, 6, 2, 2, 8, 2, 2, 4, 2, 4, 6, 4, 3, 4, 5, 2, 4, 2, 4, 9, 2, 2, 4, 4, 4, 6, 2, 2, 6, 4, 2, 4, 4, 2, 8, 2, 3, 6, 2, 6, 4, 2, 2, 4, 4, 4, 9, 2, 2, 8, 2, 2, 4, 4, 4, 6, 4, 2, 4, 4, 4, 4, 4, 2, 10, 2, 2, 8, 2, 4, 4, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Restricted growth sequence transform of A278223, the least number with the same prime signature as the n-th odd number.

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; };

A046523(n) = { my(f=vecsort(factor(n)[, 2], , 4), p); prod(i=1, #f, (p=nextprime(p+1))^f[i]); }; \\ From A046523

v305973 = rgs_transform(vector(up_to, n, A046523(n+n-1)));

A305973(n) = v305973[n];

CROSSREFS

Cf. A046523, A101296, A278223, A305901, A305983, A305985.

Sequence in context: A175778 A226182 A099774 * A290978 A142240 A284565

Adjacent sequences:  A305970 A305971 A305972 * A305974 A305975 A305976

KEYWORD

nonn

AUTHOR

Antti Karttunen, Jun 15 2018

STATUS

approved

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Last modified July 20 14:12 EDT 2019. Contains 325182 sequences. (Running on oeis4.)