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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A267237 Numbers k such that 'k-1' prepended to 'k' k times yield primes.

Original entry on oeis.org

7, 19, 989, 1187, 4183, 19607
Offset: 1

Views

Author

Mikk Heidemaa, Jan 12 2016

Keywords

Comments

a(5) produces the prime: 4182...[4183 times]4183 (16736 digits).

Examples

			7 occurs because '6' prepended 7 times to '7' produces prime (66666667).

Crossrefs

Cf. A267327.

Programs

  • Mathematica
    Select[ Range[1200], PrimeQ[ FromDigits[ StringJoin@@ ToString/@ PadLeft[{#}, #+1, #-1]]] &]

Extensions

a(6) from Michael S. Branicky, Nov 15 2024
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Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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