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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A382765 Primes that can be expressed using exactly one of each of the prime digits 2, 3, 5, 7, using concatenation and the arithmetic operations +,-,*,/,^.

Original entry on oeis.org

2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 103, 107, 113, 139, 149, 151, 163, 167, 173, 181, 197, 211, 223, 227, 229, 257, 263, 311, 353, 359, 367, 373, 379, 389, 479, 569, 571, 643, 691, 727, 733, 751, 877, 1019, 1091, 1699, 2239, 2357, 2749, 2753
Offset: 1

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Author

Zak Seidov and Robert Israel, Apr 10 2025

Keywords

Comments

Concatenation is only allowed for individual digits, not expressions, so 37 - 2^5 = 5 is allowed but (7 + 2 - 5)3 = 43 is not allowed.

Examples

			a(1) = 2 = (3 - 2) * (7 - 5).
a(2) = 3 = 2 + 3 + 5 - 7.
a(3) = 5 = 37 - 2^5.
a(4) = 7 = 2 + 3 - 5 + 7.
a(83) = 4747561509941 = 7 ^ (3 * 5) - 2.
		

Crossrefs

Cf. A382901.

Programs

  • Maple
    See link.
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