A228916 Indices of primes in sequence A108300.

1, 3, 9, 15, 39, 225, 231, 363, 687, 1299, 1335, 1809, 2367, 12735

Offset: 1

Author

Vaclav Kotesovec, Sep 08 2013

Keywords

• nonn
• hard
• more

Comments

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

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

Next term > 100000. - Tyler Busby, Mar 29 2024

Crossrefs

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

Programs

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[[#]]]&]