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A228916 Indices of primes in sequence A108300. 1
1, 3, 9, 15, 39, 225, 231, 363, 687, 1299, 1335, 1809, 2367, 12735 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Conjecture: for n>1 a(n) is a multiple of 3.

Next term > 92000.

The indices greater than 363 yield probable primes. - Vaclav Kotesovec, Oct 28 2013

LINKS

Table of n, a(n) for n=1..14.

MATHEMATICA

seq=RecurrenceTable[{a[n]==3*a[n-1]+a[n-2], a[0]==1, a[1]==5}, a, {n, 1, 1000}]; Select[Range[1000], PrimeQ[seq[[#]]]&]

CROSSREFS

Cf. A108300, A209493, A001605, A001606, A096650, A099088.

Sequence in context: A013581 A133997 A057909 * A082702 A214771 A065917

Adjacent sequences:  A228913 A228914 A228915 * A228917 A228918 A228919

KEYWORD

nonn,hard,more

AUTHOR

Vaclav Kotesovec, Sep 08 2013

STATUS

approved

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Last modified June 20 17:51 EDT 2019. Contains 324234 sequences. (Running on oeis4.)