A165555 Primes obtained from other primes by prefixing a 5.

53, 523, 541, 547, 571, 5101, 5107, 5113, 5167, 5179, 5197, 5227, 5233, 5281, 5347, 5419, 5431, 5443, 5449, 5479, 5503, 5521, 5557, 5563, 5569, 5641, 5647, 5653, 5659, 5683, 5701, 5743, 5821, 5827, 5839, 5857, 5881, 5953, 51031, 51061, 51109, 51151, 51193, 51217

Offset

1,1

Comments

The primes are considered in increasing order. Primes with the same number of digits, the difference between adjacent terms seems to be a multiple of 3.

Links

K. D. Bajpai, Table of n, a(n) for n = 1..10000

Chris Caldwell, The First 10,000 Primes

Example

5479 is a prime obtained by prefixing a 5 to the prime 479.

Maple

A165555:= n-> (parse(cat(5, ithprime(n)))): select(isprime, [seq((A165555(n), n=1..1000))]); # K. D. Bajpai, Jul 14 2017

Mathematica

Select[Table[FromDigits[Join[IntegerDigits[5], IntegerDigits[Prime[n]]]], {n, 500}], PrimeQ] (*K. D. Bajpai, Jul 14 2017 *)
Select[5*10^IntegerLength[#]+#&/@Prime[Range[200]], PrimeQ] (* Harvey P. Dale, Sep 29 2024 *)

Prog

(Magma)[k : p in PrimesUpTo (2000) | IsPrime (k) where k is Seqint (Intseq (p) cat Intseq (5))]; // K. D. Bajpai, Jul 14 2017
(PARI) lista(nn) = forprime(p=2, nn, if (isprime(q=eval(concat(5, Str(p)))), print1(q, ", "))); \\ Michel Marcus, Jul 29 2017

Crossrefs

Cf. A000040, A165243, A165292, A165444.

Sequence in context: A322043 A293089 A177120 * A201855 A112749 A245589

Adjacent sequences: A165552 A165553 A165554 * A165556 A165557 A165558

Keyword

base,nonn

Author

Parthasarathy Nambi, Sep 21 2009

Extensions

More terms from Vincenzo Librandi, Dec 02 2010

Missing term 5449 inserted by K. D. Bajpai, Jul 14 2017

Status

approved