A108114 Numbers n such that the string 3731n is the decimal expansion of a prime number.

3, 27, 51, 57, 71, 81, 83, 87, 93, 99, 107, 137, 141, 173, 207, 209, 213, 237, 251, 257, 303, 311, 333, 341, 393, 417, 443, 447, 461, 473, 477, 489, 491, 509, 513, 521, 527, 531, 549, 557, 579, 591, 593, 603, 621, 627, 683, 701, 711, 713, 731, 737, 747, 759

Offset

1,1

Comments

31 and 37 are primes.

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Example

3 is in the sequence because 37313 is prime.
99 is in the sequence because 373199 is prime.
207 is in the sequence because 3731207 is prime.

Maple

a:=proc(n) local z: z:=nops(convert(n, base, 10)): if isprime(3731*10^z+n)=true then n else fi end: seq(a(n), n=1..1000); # Emeric Deutsch, Jul 04 2005

Mathematica

Select[Range[1000], PrimeQ[3731*10^IntegerLength[#]+#]&] (* Harvey P. Dale, Aug 26 2013 *)

Prog

(Magma) [ n: n in [1..800] | IsPrime(Seqint(Intseq(n) cat [1, 3, 7, 3])) ];

Crossrefs

Sequence in context: A175545 A032418 A108163 * A172969 A147267 A071183

Adjacent sequences: A108111 A108112 A108113 * A108115 A108116 A108117

Keyword

nonn,base

Author

Parthasarathy Nambi, Jun 25 2005

Extensions

More terms from Emeric Deutsch, Jul 04 2005

Status

approved