A151413 Index at which n occurs in A160256, or -1 if n never occurs.

1, 2, 3, 4, 14, 5, 20, 6, 7, 12, 32, 11, 301, 22, 16, 8, 1065, 9

Offset

1,2

Comments

After a(19) which exceeds 10^7 but is still unknown, the sequence continues 18,24,34,a(23)=?,10,215,303,... - M. F. Hasler, May 16 2009

Links

Table of n, a(n) for n=1..18.

Formula

A160218(n) = a(A000040(n)), conjectured. - M. F. Hasler, May 16 2009

Prog

(Python)
from __future__ import division
from fractions import gcd
def A151413(n):
....if n <= 2:
........return n
....else:
........l1, l2, m, b = 2, 1, 1, {1, 2}
........for j in range(3, 10**9):
............i = m
............while True:
................if not i in b:
....................if i == n:
........................return j
....................l1, l2, m = i, l1, l1//gcd(l1, i)
....................b.add(i)
....................break
................i += m
........return "search limit reached." # Chai Wah Wu, Dec 09 2014

Crossrefs

Cf. A160256, A160218.

Sequence in context: A123215 A051855 A058070 * A031241 A064958 A067177

Adjacent sequences: A151410 A151411 A151412 * A151414 A151415 A151416

Keyword

nonn,more

Author

N. J. A. Sloane, May 16 2009

Extensions

a(13)-a(18) from Robert Gerbicz and M. F. Hasler, May 16 2009

Status

approved