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

1,2

COMMENTS

Self-inverse 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. Adams-Watters, 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, n-1, 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!=m||n==1&&m==1

newvect(80) (End)

CROSSREFS

Cf. A001221.

Cf. A100527,A159587. [From Franklin T. Adams-Watters, Apr 16 2009]

Sequence in context: A054430 A276572 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. Adams-Watters, Apr 07 2009

Values through a(72) verified by [From Franklin T. Adams-Watters, Apr 16 2009]

STATUS

approved

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Last modified November 18 19:06 EST 2017. Contains 294894 sequences.