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A151413 Index at which n occurs in A160256, or -1 if n never occurs. 3
1, 2, 3, 4, 14, 5, 20, 6, 7, 12, 32, 11, 301, 22, 16, 8, 1065, 9 (list; graph; refs; listen; history; text; internal format)
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

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Last modified March 30 20:18 EDT 2017. Contains 284302 sequences.