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.

A378139 Smallest prime number such that the number of distinct prime factors with multiplicity of its 9's complement is equal to n. If no such number exists, return -1.

Original entry on oeis.org

2, 3, 23, 11, 19, 263, 167, 103, 487, 1039, 7951, 5903, 28319, 107071, 67231, 590399, 180799, 344639, 1480319, 12181759, 4757119, 10871039, 1611391, 140167679, 203082239, 228248063, 530237951, 1812718591, 5302379519, 13295347711, 12758476799, 132953477119, 1410065407
Offset: 1

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Author

Jean-Marc Rebert, Jan 08 2025

Keywords

Examples

			2 is prime, 9-2 = 7 and bigomega(7) = 1.
		

Crossrefs

Programs

  • PARI
    nc(n) = my(e=length(Str(n))); 10^e-1 - n; \\ A061601
    a(n) = my(p=2); while (bigomega(nc(p)) != n, p = nextprime(p+1)); p; \\ Michel Marcus, Jan 08 2025