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A320585 Primes whose first digit is prime. 1
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..55.

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

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Last modified October 21 22:47 EDT 2019. Contains 328315 sequences. (Running on oeis4.)