A320585 Primes whose first digit is prime.

2, 3, 5, 7, 23, 29, 31, 37, 53, 59, 71, 73, 79, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 503, 509, 521, 523, 541, 547, 557, 563, 569, 571

Offset

1,1

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Maple

2, 3, 5, 7, seq(seq(op(select(isprime, [seq(i*10^(d-1)+j, j=1..10^(d-1)-1, 2)])), i=[2, 3, 5, 7]), d=1..4); # Robert Israel, Apr 02 2020

Mathematica

Select[Range[575], PrimeQ[#] && PrimeQ[IntegerDigits[#][[1]]] &] (* Amiram Eldar, Nov 11 2018 *)

Prog

(PARI) isok(n) = isprime(n) && isprime(digits(n)[1]); \\ Michel Marcus, Oct 17 2018

Crossrefs

Intersection of A000040 and A320584 (numbers whose first digit is prime).

Sequence in context: A124673 A024776 A069867 * A024770 A038603 A106116

Adjacent sequences: A320582 A320583 A320584 * A320586 A320587 A320588

Keyword

nonn,base

Author

Kritsada Moomuang, Oct 16 2018

Status

approved