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A139188 Smallest twin prime member A006512 of the form k!/n + 1. 2
7, 13, 241, 7, 7983361, 5, 453601, 13, 61, 2689, 2688996956405760001, 7, 241, 31, 44960029111104307201, 134401, 181, 5, 1153, 100801, 536481792001, 19, 141523201, 1313375283986387731246850697141608641462272000000001, 7561, 8065829222532112711680001 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Given n, the sequence shows the smallest A006512(j) =a(n) of the form k!/n-1.

The associated lower twin prime is A139187(n) = A001359(j) = a(n)-2,

and the associated factorial index is k(n) = A139186(n).

LINKS

Table of n, a(n) for n=1..26.

FORMULA

a(n) = A139187(n)+2 = A000142(A139186(n))/n+1 .

MATHEMATICA

a = {}; Do[k = 1; While[ ! (PrimeQ[(k! - n)/n] && PrimeQ[(k! + n)/n]), k++ ]; AppendTo[a, (k! + n)/n], {n, 1, 6}]; a (*Artur Jasinski*)

CROSSREFS

Cf. A139186, A139187.

Sequence in context: A243368 A317209 A084963 * A064119 A224984 A228030

Adjacent sequences:  A139185 A139186 A139187 * A139189 A139190 A139191

KEYWORD

nonn

AUTHOR

Artur Jasinski, Apr 11 2008

EXTENSIONS

Edited and extended by R. J. Mathar, Sep 22 2009

STATUS

approved

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Last modified January 24 01:05 EST 2020. Contains 331178 sequences. (Running on oeis4.)