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A144946 Least a(n) such that p(n)#*(p(n)#+a(n))-1 is prime with p(i)#=i-th primorial. 4
1, 1, 1, 2, 1, 1, 8, 21, 5, 4, 4, 4, 32, 4, 16, 7, 9, 1, 14, 5, 32, 22, 35, 6, 21, 11, 22, 3, 72, 48, 20, 1, 8, 1, 36, 30, 32, 6, 26, 14, 2, 22, 32, 6, 48, 37, 2, 58, 1, 74 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

As n increases sum(a(i)) for i=1 to n tends to e^gamma/2*n*(n+1)/2, notice that n*(n+1)/2 is triangular number. [From Pierre CAMI, Oct 16 2008]

LINKS

Pierre CAMI, Table of n, a(n) for n = 1..500

EXAMPLE

2*(2+1)-1=5 prime so a(1)=1 6*(6+1)-1=41 prime so a(2)=1 30*(31)-1=929 prime so a(3)=1.

CROSSREFS

Cf. A144947

Sequence in context: A225848 A165889 A087127 * A260374 A157109 A185814

Adjacent sequences:  A144943 A144944 A144945 * A144947 A144948 A144949

KEYWORD

nonn

AUTHOR

Pierre CAMI, Sep 26 2008, Oct 16 2008

STATUS

approved

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Last modified January 15 23:42 EST 2019. Contains 319184 sequences. (Running on oeis4.)