A084384 a(1) = 2; a(n+1) = smallest k > a(n) that is divisible by at most (1/2)*[tau(k)] previous terms.

2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 14, 15, 17, 19, 21, 22, 23, 25, 26, 27, 29, 31, 32, 33, 34, 35, 37, 38, 39, 41, 43, 46, 47, 48, 49, 51, 53, 55, 57, 58, 59, 61, 62, 65, 67, 69, 71, 72, 73, 74, 77, 79, 80, 82, 83, 85, 86, 87, 89, 91, 93, 94, 95, 97, 101, 103, 106, 107, 108

Offset

1,1

Comments

Membership in this sequence depends only on the prime signature, see PARI script. - Charles R Greathouse IV, Oct 19 2015

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Example

12 is not a member as tau(12) = 6 and there are four terms 2,3,4 and 6 that divide 12.

Prog

(PARI) has(f)=f=select(n->n, f); if(#f==0, return(0)); if(#f==1 && f[1]<4, return(1)); my(t=prod(i=1, #f, f[i]+1)\2); forvec(x=vector(#f, i, [0, f[i]]), if(x==f, return(1)); t-=has(x); if(t<0, return(0)))
is(n)=has(factor(n)[, 2]~) \\ Charles R Greathouse IV, Oct 19 2015

Crossrefs

Sequence in context: A317468 A329481 A261355 * A119885 A007964 A095135

Adjacent sequences: A084381 A084382 A084383 * A084385 A084386 A084387

Keyword

nonn

Author

Amarnath Murthy, May 29 2003

Extensions

More terms from David Wasserman, Dec 20 2004

Status

approved