

A232271


Start with positive integers (A000027), and at each step n >= 1 subtract from the term at position n + a(n) the value a(n).


0



1, 1, 2, 4, 3, 6, 7, 1, 8, 10, 11, 6, 13, 7, 15, 16, 9, 12, 30, 10, 14, 11, 23, 24, 25, 4, 27, 28, 29, 11, 31, 16, 22, 34, 21, 36, 37, 19, 39, 40, 41, 42, 43, 44, 45, 23, 47, 8, 49, 25, 51, 52, 53, 27, 34, 1, 38, 29, 59, 60, 61, 31, 63, 64, 65, 66, 67, 34, 307, 70, 71
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OFFSET

1,3


COMMENTS

The first 71 terms are correct if the following conjecture is true: n+a(n)<=0 or n+a(n)>71 for n >= 2^30.
The sequence of negative terms begins: 11, 1, 261, 11, 253, 319, 341, 407, 451, 528, 329, 371, 29, 31, 649, 619, 427, 737, 37, ...
Indices of negative terms: 30, 56, 330, 616, 690, 870, 930, 1110, 1230, 1288, 1410, 1590, 1624, 1736, 1770, 1820, 1830, 2010, 2072, ...
Numbers n such that a(n)=n: 1, 4, 6, 7, 10, 11, 13, 15, 16, 23, 24, 25, 27, 28, 29, 31, 34, 36, 37, 39, 40, 41, 42, 43, 44, 45, ...
The sequence of numbers n such that n+a(n)<0 begins: 1485264, 2029290, 6156150, 6872250, 8338512, 8769090, 10420410, 13448490, 16654110, 25894770, ...


LINKS

Table of n, a(n) for n=1..71.


PROG

(Python)
TOP = 2**30 # if enough RAM
a = [1]*TOP
for n in range(1, TOP):
a[n]=n
for n in range(1, TOP):
if n+a[n]<TOP and n+a[n]>0: a[n+a[n]] = a[n]
for n in range(1, 1000):
print str(a[n])+', ',


CROSSREFS

Cf. A000027, A136119, A137319, A137417, A137418, A137894.
Sequence in context: A235451 A039819 A242424 * A194277 A226246 A216623
Adjacent sequences: A232268 A232269 A232270 * A232272 A232273 A232274


KEYWORD

sign


AUTHOR

Alex Ratushnyak, Nov 22 2013


EXTENSIONS

Corrected by Alex Ratushnyak, Dec 28 2013


STATUS

approved



