A130101 Primes prime(n) such that 10*prime(n)+prime(n+1) is not prime.

3, 5, 7, 11, 13, 17, 19, 23, 29, 37, 41, 43, 53, 59, 67, 71, 79, 89, 97, 101, 103, 107, 109, 113, 127, 137, 139, 149, 163, 167, 173, 179, 181, 191, 193, 197, 199, 223, 227, 229, 233, 239, 241, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 347

Offset

1,1

Links

Table of n, a(n) for n=1..57.

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

Cf. A129900.

Sequence in context: A155058 A007703 A002556 * A130057 A226181 A363286

Adjacent sequences: A130098 A130099 A130100 * A130102 A130103 A130104

Keyword

nonn

Author

Jani Melik, Aug 01 2007

Status

approved