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A255771 Number of distinct prime factors of A220294(n). 4
1, 1, 1, 2, 2, 1, 2, 2, 4, 2, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,4
COMMENTS
These are the first differences of A255770.
REFERENCES
Arthur Engel, Problem-Solving Strategies, Springer, 1998, pages 121-122 (E3, said to be a "recent competition problem from the former USSR").
LINKS
EXAMPLE
A220294(0) = 3 so a(0) = 1.
A220294(1) = 13 so a(1) = 1.
A220294(2) = 241 so a(2) = 1.
A220294(3) = 97*673 so a(3) = 2.
A220294(4) = 193*22253377 so a(4) = 2.
CROSSREFS
Sequence in context: A070215 A071457 A227782 * A334590 A115034 A253193
KEYWORD
nonn,hard,more
AUTHOR
Hans Havermann, Mar 06 2015
EXTENSIONS
Offset changed by Arkadiusz Wesolowski, Aug 01 2016
a(9) was found in 2008 by Geoffrey Reynolds. a(10) was found by Anders Björn and Hans Riesel. - Arkadiusz Wesolowski, Aug 02 2016
STATUS
approved

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Last modified March 28 20:05 EDT 2024. Contains 371254 sequences. (Running on oeis4.)