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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A111479 a(n) = least positive number such that (2 Concat Concat_{k=1}^n Repeat(A045572(n), a(n))) is a prime. A045572 = odd numbers not divisible by 5.

Original entry on oeis.org

2, 1, 4, 11, 3, 617, 96, 1213, 1965
Offset: 1

Views

Author

Amarnath Murthy, Aug 05 2005

Keywords

Comments

Concat is the operator that concatenates two numbers as decimal strings and Repeat returns the number obtained by concatenating the first argument to itself the second argument number of times.

Examples

			21 is not a prime, but 211 is, so a(1)=2.
211,2113,21137777 are all primes. 21137777 is a prime obtained as 2 followed by two 1's, one 3 and four 7's, so a(2) = 4.

Crossrefs

Cf. A111471, A111472, A111473, A111475, A111477, A111478, A111480.

Extensions

Edited by Franklin T. Adams-Watters, Aug 29 2006.
Corrected and extended by Max Alekseyev, May 21 2009
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Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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