

A193298


GicaPanaitopol recursion: a(1) = 1; a(n+1) = 2*a(n) if a(n) <= n; otherwise a(n+1) = a(n)  1.


5



1, 2, 4, 3, 6, 5, 10, 9, 8, 16, 15, 14, 13, 26, 25, 24, 23, 22, 21, 20, 40, 39, 38, 37, 36, 35, 34, 33, 32, 31, 30, 60, 59, 58, 57, 56, 55, 54, 53, 52, 51, 50, 49, 48, 47, 46, 92, 91, 90, 89, 88, 87, 86, 85, 84, 83, 82, 81, 80, 79, 78, 77, 76, 75, 74, 73, 72, 71, 70, 69
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OFFSET

1,2


COMMENTS

Using the Prime Number Theorem, Gica and Panaitopol show that the sequence contains infinitely many primes.


REFERENCES

A. Gica and L. Panaitopol, An application of the prime element theorem, Gazeta Matematica 21(100), No. 2 (2003), 113115.


LINKS

T. D. Noe, Table of n, a(n) for n = 1..10000


EXAMPLE

The terms occur in disjoint blocks of decreasing consecutive numbers: 1; 2; 4, 3; 6, 5; 10, 9, 8; 16, 15, 14, 13; 26, 25, 24, 23, 22, 21, 20; . . .


MATHEMATICA

a[1] = 1; a[n_] := a[n] = If[a[n1] <= n1, 2*a[n1], a[n1]1]; Table[a[n], {n, 100}]


CROSSREFS

Cf. A193299 (sorted sequence), A193300 (subset of primes), A193301 (complement of sorted sequence).
Sequence in context: A132666 A116533 A087559 * A168007 A328108 A091850
Adjacent sequences: A193295 A193296 A193297 * A193299 A193300 A193301


KEYWORD

nonn


AUTHOR

Jonathan Sondow, Jul 21 2011


STATUS

approved



