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.

A360041 Prime numbers missing from A359137: prime numbers for which none of the nontrivial permutations of its digits (not 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, 103, 109, 257, 263, 269, 307, 401, 409, 431, 487, 503, 509, 523, 541, 601, 607, 809, 827, 829, 853, 859, 2017, 2087, 2861, 4027, 4051, 4079, 4801, 5021, 5209, 5623, 5849, 6047, 6053, 6803, 8053, 8059
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.

Examples

			The nontrivial permutations of the digits of 607 (not permitting leading zeros) are:
  670 = 2 * 5 * 67,
  706 = 2 * 353,
  760 = 2^3 * 5 * 19,
so 607 belongs to the sequence.
		

Crossrefs

Programs

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