OFFSET
1,1
EXAMPLE
a(11)=41 because 41 is prime, the nextprime is 43 and 10*41+43=453, 453 = 3*151 is not prime,
a(12)=43 because 43 is prime, the nextprime is 47 and 10*43+47=477, 477 = 3^(2)*53 is not prime,
a(13)=53 because 53 is prime, the nextprime is 59 and 10*53+59=589, 589 = 19*31 is not prime, ...
MAPLE
ts_p5_02:=proc(n) local a, b, i, ans; ans := [ ]: for i from 1 to n do a := 10*ithprime(i)+ithprime(i+1): if (isprime(a)=false) then ans := [ op(ans), ithprime(i) ]: fi od; RETURN(ans) end: ts_p5_02(300);
CROSSREFS
KEYWORD
nonn
AUTHOR
Jani Melik, Aug 01 2007
STATUS
approved