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.

A360040 Prime numbers missing from A359136: prime numbers for which none of the nontrivial permutations of its digits (permitting leading zeros) produces a prime number.

Original entry on oeis.org

2, 3, 5, 7, 19, 23, 29, 41, 43, 47, 53, 59, 61, 67, 83, 89, 257, 263, 269, 409, 431, 487, 523, 541, 827, 829, 853, 859, 2861, 4027, 4801, 5209, 5623, 5849
Offset: 1

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Author

Rémy Sigrist, Jan 23 2023

Keywords

Comments

Any prime number p >= 10^11 has necessarily a duplicate digit, say that appears at positions i and j. Applying the nontrivial permutation (i j) to the digits of p yields a prime number (p itself), hence p does not belong to the sequence and the sequence is finite.
All terms belong to A360041.

Crossrefs

Programs

  • PARI
    is(p) = { my (d=digits(p)); if (#d > #Set(d), return (0), forperm (vecsort(d), t, my (q=fromdigits(Vec(t))); if (p!=q && isprime(q), return (0))); return (1)) }

Formula

The nontrivial permutations of the digits of 409 (permitting leading zeros) are:
049 = 7^2,
094 = 2 * 47,
490 = 2 * 5 * 7^2,
904 = 2^3 * 113,
940 = 2^2 * 5 * 47,
so 409 belongs to the sequence.