OFFSET
1,1
COMMENTS
a(2)=a(3)=13, a(5)=a(6)=73, ... a(29)=a(30)=...=a(43)=9098, ... . A244436 gives numbers k such that a(k) is not in the set {a(k-1), a(k+1)}.
LINKS
Robert Israel, Table of n, a(n) for n = 1..164
MAPLE
M:= 0: R:= NULL:
for m from 2 while M < 100 do
for i from 0 while not isprime(2*i*m-1) do od:
if i-1 > M then R:= R, m$(i-1-M); M:= i-1; fi;
od:
R; # Robert Israel, May 03 2021
PROG
(PARI) isok(n, m) = for(k=1, n, my(x=2*k*m-1); if ((x==1) || isprime(x), return(0))); return (1);
a(n) = my(m=1); while(!isok(n, m), m++); m; \\ Michel Marcus, May 04 2021
CROSSREFS
KEYWORD
nonn,changed
AUTHOR
Farideh Firoozbakht, Jul 19 2014
STATUS
approved