A159587 a(n) is the smallest number not yet in the sequence with the same number of distinct prime divisors as n, but relatively prime to n.

1, 3, 2, 5, 4, 35, 8, 7, 11, 21, 9, 55, 16, 15, 14, 13, 19, 65, 17, 33, 10, 39, 25, 77, 23, 45, 29, 51, 27, 1001, 32, 31, 20, 57, 6, 85, 41, 63, 22, 69, 37, 715, 47, 75, 26, 87, 43, 91, 53, 93, 28, 95, 49, 115, 12, 99, 34, 111, 61, 1309, 59, 117, 38, 67, 18, 455, 64, 123, 40, 429

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..10000

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

Crossrefs

Cf. A001221, A094681, A159588.

Sequence in context: A366264 A329544 A095006 * A369992 A124732 A167552

Adjacent sequences: A159584 A159585 A159586 * A159588 A159589 A159590

Keyword

nonn

Author

Franklin T. Adams-Watters, Apr 16 2009

Status

approved