cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A320585 Primes whose first digit is prime.

Original entry on oeis.org

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

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Author

Kritsada Moomuang, Oct 16 2018

Keywords

Crossrefs

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

Programs

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