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

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

Offset

1,3

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

David Broadhurst, Table of n, a(n) for n = 1..94

Hans Havermann and David Broadhurst, Crandall Numbers Factored

Formula

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

Prog

(PARI) a(n)=A006530(A262961(n)) \\ M. F. Hasler, Oct 17 2015

Crossrefs

Cf. A262961.

Sequence in context: A155762 A307480 A062611 * A270585 A041505 A116629

Adjacent sequences: A263410 A263411 A263412 * A263414 A263415 A263416

Keyword

nonn,hard

Author

M. F. Hasler, Oct 17 2015

Status

approved