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A080735 a(1)=1, then a(n)=2*a(n-1) if a(n-1) is prime, a(n)=a(n-1)+1 otherwise. 2
1, 2, 4, 5, 10, 11, 22, 23, 46, 47, 94, 95, 96, 97, 194, 195, 196, 197, 394, 395, 396, 397, 794, 795, 796, 797, 1594, 1595, 1596, 1597, 3194, 3195, 3196, 3197, 3198, 3199, 3200, 3201, 3202, 3203, 6406, 6407, 6408, 6409, 6410, 6411, 6412, 6413, 6414, 6415, 6416 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Conjectures: (Strong) Let x,y be 2 positive integers and define a(n) as a(1)=1, a(n)=x*a(n-1) if a(n-1) is prime, a(n)=a(n-1)+y otherwise; then limit n ->infinity log(a(n))/sqrt(n)=C(x,y) exists. (Weak) log(a(n))/sqrt(n) is bounded.
LINKS
FORMULA
It seems that log(a(n))/sqrt(n) -> C, a constant around 1.3.....
MATHEMATICA
NestList[If[PrimeQ[#], 2#, #+1]&, 1, 50] (* Harvey P. Dale, Aug 26 2013 *)
PROG
(PARI) u=1; for(n=2, 100, v=if(isprime(u), u+1, 2*u); u=v; print1(v, ", "))
CROSSREFS
Cf. A163962.
Sequence in context: A328009 A128216 A299322 * A091856 A083416 A022770
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Mar 08 2003
STATUS
approved

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Last modified May 30 12:55 EDT 2023. Contains 363050 sequences. (Running on oeis4.)