A152870 Indices of primes in the Padovan sequence A000931.

8, 9, 10, 12, 13, 19, 24, 35, 42, 89, 133, 474, 671, 1267, 1578, 2008, 2215, 2294, 4168, 5558, 6572, 8566, 11235, 18742, 35839, 44264, 536490, 727739

Offset: 1

Author

Roger L. Bagula, Dec 14 2008

Keywords

• nonn
• more

Crossrefs

Cf. A000931, A001605, A100891, A112882.

Programs

Mathematica

a[0] = 1; a[1] = 0; a[2] = 0;
a[n_] := a[n] = a[n - 2] + a[n - 3];
Flatten[Table[If[PrimeQ[a[n]], n, {}], {n, 0, 10000}]]

PARI

v=[1,1,1];for(n=8,1e4,v=[v[2],v[3],v[1]+v[2]];if(ispseudoprime(v[3]),print1(n", "))) \\ Charles R Greathouse IV, Nov 07 2011

Formula

a(n) = A112882(n) + 5. - Amiram Eldar, Nov 10 2024

Extensions

a(23)-a(26) from Charles R Greathouse IV, Nov 07 2011

a(27)-a(28) calculated from the data at A112882 by Amiram Eldar, Nov 10 2024