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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A263413 Largest prime (or noncomposite) factor of the Crandall number A262961(n).

Original entry on oeis.org

0, 1, 2, 5, 151, 661, 521, 49993, 858868651, 115523, 72920757563, 3844109, 1637177, 7158605959, 17024617, 13062611, 66113257898351335849, 599880481206897379, 745125370039, 4314028165895642655831229, 30699710580827, 1744795596758086587163381, 2463356705098399667815003
Offset: 1

Views

Author

M. F. Hasler, Oct 17 2015

Keywords

Comments

Computed up to n = 94 by David Broadhurst, and independently up to n = 67 by Hans Havermann and M. F. Hasler.
At n = 95 and n = 96 we have composite factors of 157 digits with probably no divisor less than 50 digits. - David Broadhurst, Oct 17 2015

Links

Crossrefs

Cf. A262961.

Programs

Formula

a(n) = A006530(A262961(n)).

A265079 Numbers n such that the Crandall number C = A262961(n) has exactly one prime divisor p >= n/2.

Original entry on oeis.org

3, 5, 7, 9, 11, 33, 36, 49, 453, 727, 1560, 1569, 1627, 5078, 6605, 17663, 27281, 29298, 29708, 39509, 98653
Offset: 1

Views

Author

N. J. A. Sloane, Dec 30 2015

Keywords

Comments

If a Crandall number C = A262961(n) is an even semiprime, then n is a term of this sequence. - Altug Alkan, Dec 30 2015

Examples

			5 is a term because A262961(5) = 302 and its prime divisors are 2, 151 and only 151 >= 5/2.

Links

Crossrefs

Cf. A262961.
Showing 1-2 of 2 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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