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.

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A383919 Primes made up of 0's and seven 1's only.

Original entry on oeis.org

11110111, 11111101, 101101111, 101111011, 110111011, 111010111, 1001110111, 1010011111, 1011110011, 1100101111, 1101010111, 1101110011, 1110011101, 1110110011, 1111100101, 1111110001, 10010110111, 10011101011, 10011110101, 10100111101, 10111001011, 10111110001, 11001011101
Offset: 1

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Author

René-Louis Clerc, May 15 2025

Keywords

Comments

Expression of the primes that are 0-successors of the preprime 1111111 (= 239*4649); they constitute the infinite set of secondary primes with seven 1's and zeros denoted {1111111} (Definitions 1, 2, 3, 4 of Clerc).

Crossrefs

Intersection of A020449 and A062337.

Programs

  • PARI
    list(M) = for(i=3, M, for(j=2, i-1, for(k=1, j-1, for(r=1, k-1, for(l=1, r-1, for(m=1, l-1, my(p=10^i+10^j+10^k+10^r+10^l+10^m+1); isprime(p) && print1(p, ", ")))))))
    
  • Python
    from itertools import count, islice
    from sympy import isprime
    def A383919_gen(): # generator of terms
        for a in count(6):
            for b in range(5,a):
                for c in range(4,b):
                    for d in range(3,c):
                        for e in range(2,d):
                            for f in range(1,e):
                                if isprime(p:=10**a+10**b+10**c+10**d+10**e+10**f|1):
                                    yield(p)
    A383919_list = list(islice(A383919_gen(),23)) # Chai Wah Wu, May 28 2025
Previous Showing 11-11 of 11 results.