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A078305 Numbers n such that A004154(n) - 1 is prime. 4
3, 4, 5, 6, 7, 13, 14, 19, 20, 28, 37, 99, 100, 108, 141, 304, 442, 682 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Some of the larger entries may only correspond to probable primes.

LINKS

Table of n, a(n) for n=1..18.

MATHEMATICA

f[n_] := n!/10^Sum[ Floor[n/5^k], {k, 1, Log[10, n] + 1}]; Do[ If[ PrimeQ[ f[n] - 1], Print[n]], {n, 1, 750}]

CROSSREFS

Cf. A004154, A078154, A078203, A078190.

Sequence in context: A052002 A247636 A070916 * A235324 A330373 A072599

Adjacent sequences:  A078302 A078303 A078304 * A078306 A078307 A078308

KEYWORD

nonn

AUTHOR

Cino Hilliard, Dec 23 2002

EXTENSIONS

Extended by Robert G. Wilson v and Jason Earls, Dec 24 2002

STATUS

approved

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Last modified January 19 18:13 EST 2020. Contains 331051 sequences. (Running on oeis4.)