

A180131


Smallest k such that k*3^n is a sum of two successive primes.


9



5, 4, 2, 6, 2, 10, 20, 26, 22, 10, 16, 8, 8, 72, 24, 8, 18, 6, 2, 6, 2, 10, 20, 20, 22, 20, 52, 50, 104, 118, 84, 28, 38, 306, 102, 34, 100, 50, 30, 10, 192, 64, 46, 66, 22, 220, 84, 28, 176, 88, 30, 10, 8, 152, 292, 98, 82, 124, 160, 206, 106, 106, 160, 128, 78, 26, 110, 80
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OFFSET

0,1


COMMENTS

If a(n) == 0 (mod 3), then a(n+1) = a(n)/3.
Records: 5, 6, 10, 20, 26, 72, 104, 118, 306, 320, 348, 572, 824, 828, 972, 1054, 1110, 1540, ..., .
Corresponding primes which are twin primes for n = 0, 1, 10, 13, 14, 15, 22, 102, ..., .


LINKS

Robert G. Wilson v, Table of n, a(n) for n = 0..700


MATHEMATICA

f[n_] := Block[{k = 1, j = 3^n/2}, While[ h = k*j; PrimeQ@h  NextPrime[h, 1] + NextPrime@h != 2 h, k++ ]; k]; Array[f, 80, 0]


CROSSREFS

Cf. A180130, A180132, A180133, A180134, A179975, A180135, A180136, A180137, A180138.
Sequence in context: A094778 A260849 A246746 * A257972 A222307 A175838
Adjacent sequences: A180128 A180129 A180130 * A180132 A180133 A180134


KEYWORD

base,nonn


AUTHOR

Zak Seidov & Robert G. Wilson v, Aug 15 2010


STATUS

approved



