A104576 Indices of primes in A001644 (the Lucas 3-step numbers).

2, 3, 4, 7, 8, 9, 10, 12, 20, 30, 33, 66, 76, 77, 82, 87, 98, 180, 205, 360, 553, 719, 766, 1390, 1879, 1999, 4033, 5620, 16506, 17436, 23676, 24428, 27758, 31932, 58199, 67661, 85040, 102023, 185595

Offset: 1

Author

T. D. Noe, Mar 16 2005

Keywords

• nonn
• more

Comments

The sequence of generalized tribonacci numbers is defined as beginning with 1, 3, 7. Subsequent terms are the sum of the previous three terms. Note that the sequence of these generalized tribonacci numbers has many more primes than the tribonacci sequence A000073 (whose prime indices are in A092835).

a(40) > 2*10^5. - Robert Price, Dec 24 2013

Links

• Tony D. Noe and Jonathan Vos Post, Primes in Fibonacci n-step and Lucas n-step Sequences, J. of Integer Sequences, Vol. 8 (2005), Article 05.4.4

Crossrefs

Cf. A104577 (indices of prime generalized tetranacci numbers).

Cf. A000073, A001644, A092835, A105762.

Formula

A001644(a(n)) = A105762(n). - Arthur O'Dwyer, Jul 26 2024

Extensions

a(37)-a(39) from Robert Price, Dec 24 2013

Name clarified by Arthur O'Dwyer, Jul 25 2024