A159588 a(n) is the smallest number not yet in the sequence with the same number of prime factors as n (with repetition), but relatively prime to n.

1, 3, 2, 9, 7, 25, 5, 27, 4, 21, 13, 125, 11, 15, 14, 81, 19, 175, 17, 63, 10, 35, 29, 625, 6, 33, 8, 45, 23, 343, 37, 243, 26, 39, 22, 875, 31, 49, 34, 189, 43, 275, 41, 75, 28, 51, 53, 3125, 38, 99, 46, 105, 47, 1225, 57, 135, 55, 65, 61, 2401, 59, 69, 20, 729, 58, 245, 71

Offset

1,2

Comments

This is a self-inverse permutation of the positive integers.

Links

Rémy Sigrist, Table of n, a(n) for n = 1..5000

Rémy Sigrist, Scatterplot of (n, a(n)) for n, a(n) <= 25000

Prog

(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)=bigomega(n)==bigomega(m)&&gcd(n, m)==1
newvect(80)

Crossrefs

Cf. A001222, A100527, A159587.

Sequence in context: A118306 A237651 A124003 * A321572 A118045 A276023

Adjacent sequences: A159585 A159586 A159587 * A159589 A159590 A159591

Keyword

nonn

Author

Franklin T. Adams-Watters, Apr 16 2009

Status

approved