

A094681


Smallest number <>n, not occurring earlier and having as many distinct prime factors as n has, with a(1) = 1.


2



1, 3, 2, 5, 4, 10, 8, 7, 11, 6, 9, 14, 16, 12, 18, 13, 19, 15, 17, 21, 20, 24, 25, 22, 23, 28, 29, 26, 27, 42, 32, 31, 34, 33, 36, 35, 41, 39, 38, 44, 37, 30, 47, 40, 46, 45, 43, 50, 53, 48, 52, 51, 49, 55, 54, 57, 56, 62, 61, 66, 59, 58, 65, 67, 63, 60, 64, 69, 68, 78, 73, 74
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OFFSET

1,2


COMMENTS

Selfinverse integer permutation: a(a(n))=n.


LINKS

Table of n, a(n) for n=1..72.
Index entries for sequences that are permutations of the natural numbers


PROG

Contribution from Franklin T. AdamsWatters, Apr 16 2009: (Start)
(PARI) invect(v, n, x)=for(i=1, n, if(v[i]==x, return(1))); 0
nextnew(v, n)=local(k); k=1; while(!R(n, k)invect(v, n1, k), k++); k
newvect(n)=local(v); v=vector(n); for(k=1, n, v[k]=nextnew(v, k)); v
R(n, m)=omega(n)==omega(m)&&n!=mn==1&&m==1
newvect(80) (End)


CROSSREFS

Cf. A001221.
Cf. A100527,A159587. [From Franklin T. AdamsWatters, Apr 16 2009]
Sequence in context: A276572 A330311 A204891 * A054158 A054080 A164379
Adjacent sequences: A094678 A094679 A094680 * A094682 A094683 A094684


KEYWORD

nonn


AUTHOR

Reinhard Zumkeller, Jun 08 2004


EXTENSIONS

Description corrected by Franklin T. AdamsWatters, Apr 07 2009
Values through a(72) verified by [From Franklin T. AdamsWatters, Apr 16 2009]


STATUS

approved



