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A179279 Composite numbers n such that (Bell(n+1)-Bell(n)) mod n = 1. 0
4, 28, 40, 343 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The congruence is true for all primes n. Bell(n) is the sequence A000110. Tested up to n=5000.

LINKS

Table of n, a(n) for n=1..4.

EXAMPLE

For n=4, (Bell(5)-Bell(4))%4 = (52-15)%4 = 37%4 = 1, but 4 is not prime.

MATHEMATICA

fQ[n_] := ! PrimeQ@n && Mod[BellB[n + 1] - BellB[n], n] == 1; k = 1; lst = {}; While[k < 9201, If[fQ@k, AppendTo[lst, k]; Print@k]; k++ ]; lst (* Robert G. Wilson v, Jul 28 2010 *)

CROSSREFS

Sequence in context: A043074 A137314 A032405 * A061428 A069518 A151912

Adjacent sequences:  A179276 A179277 A179278 * A179280 A179281 A179282

KEYWORD

nonn,more

AUTHOR

Jean-Claude Arbaut, Jul 08 2010

STATUS

approved

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Last modified February 25 11:08 EST 2018. Contains 299653 sequences. (Running on oeis4.)